DIA0T1SK 



IMATOMACE.S. 



DIASTASE, substance fanned during the termination of plants. 

 It can be artificially prepared by reducing freshly germinated barley 

 into a pulp, with half iU weight of water, and then prawing out the 

 liquor strongly. To the clear liquid jul sufficient alcohol is to be 

 added to destroy iU rUcjdity and allow of iU being Bltered ; by tlii.i 

 an aaotiatd substance U precipitated, which mimt be considered as 

 vegetable albumen, since it coagulates at 167" Fahr. Having sepa- 

 rated this, alcohol U again to be added u long as the liquid become* 

 turbid; the precipitate U to be purified by solution in water and 

 precipitation by alcohol repeatedly ; the precipitate is at last to be 

 drinl in thin layers upon glass at a temperature between 101* and 

 123- Fahr. 



The properties of diastase are the following : It is solid, white, 

 not crystalline, soluble in water, but insoluble in alcohol unless it be 

 weak; the aqueous solution is nearly tasteless, and without any 

 chemical action, not precipitating subacetate of lead. The aqueous 

 solution quickly changes, becoming acid : dry diastase undergoes 

 the same change in a longer time, but when boiled in water the 

 alteration is immediate. Common malt is stated in general not to 

 contain more than 1 -500th of ita weight of diastase : one part of it 

 U sufficient to convert 2000 parts of starch, thickeucd with water, 

 into a mixture consisting of much dextrine and a little sugar. It has 

 not yet been obtained absolutely pure. There can be little doubt 

 that diastase is one of the forms of protein ; and its reaction upon 

 starch is not different from that which takes place with some other 

 forms of the same substance. Schleiden includes it amongst the 

 nitrogenous substances of plants, to which he gives the name Schleim 

 (mucus). 



(Schleiden, Principle* of Scienttfe Botany, p. 23.) 



DIA'STYLIS, a genus of Crustacean Animals established by M. 

 Say. 



It has the following characters. Four antenna) placed nearly on 

 the same line ; the intermediate antenna; bifid, having a peduncle of 

 three joints, the external simple, with the first joint long, and without 

 a scale. External jaw-feet very large, pediform, very much approxi- 

 mated to the front, with the first joint long and compressed, and the 

 others very small, cylindrical, and nearly equal. Corselet smooth, of 

 six segments, of which the first, larger than all the others together, is 

 terminated anteriorly by a short obtuse triangular rostrum, crene- 

 lated on ita lateral edges. Six pairs of bifid feet ; those of the first 

 pair truncated at the end, and shorter than the external jaw-feet; 

 those of the second terminated in a point ; those of the third, fourth, 

 and fifth pairs raised, pointed, without a nail, and terminated by 

 strong hairs. Abdomen narrower than the thorax, formed of six 

 segments, the last two of which support the natatory feet. Tail 

 biarticulated, provided on each side of the first segment with a single 

 bifid style, and on the extremity of the second with a simple cylin- 

 drical style. 



1>. arrnariut. Length one-fifth of an inch. It is an inhabitant of 

 the coasts of Georgia and Florida. 



M. Say is of opinion that the Cancer tcorpionide* of Montagu, from 

 the English coasts, and the C. tca of Qmelin, from those of Norway, 

 ought to be referred to this genus. 



JJIATOMACE^E, or DIATOME^E, a group of organised beings 

 which naturalists have placed in the animal and vegetable kingdoms, 

 according as they have regarded their structures as most allied to the 

 one kingdom or the other. These organisms consist of a single cell, 

 and are remarkable for possessing a hard shell-valve or frustule, 

 which is composed of silex or flint, and which remains permanent 

 after ita organic tissues have perished. 



The following is a definition of this group of beings by one of the 

 most recent writers on this subject : Plant a frustule ; consisting of 

 a unilocular or imperfectly septate cell, invested with a bivalve sili- 

 ceous epidermis. Qemmiparous increase, by self-division; during 

 which process the cell secretes a more or less siliceous connecting 

 membrane. Reproduction, by conjugation, and the formation of 

 sporangia. (W. Smith.) 



The Dialomactff are endowed with the power of motion ; and when 

 this function was supposed to be peculiar to the animal kingdom, it 

 is not to be wondered at that the first observers of these organisms 

 referred them to the animal kingdom. Khrenlierg, in his great work 

 on the ' Infusorial Animalcules,' greatly enlarged our knowledge of 

 this family, and added to the forms that were already known. He 

 regarded them, u well as the Dtmidiar, and other beings which are 

 now generally referred to the vegetable kingdom, as animals. The 

 following an the principal points on which he relied for assigning to 

 them this position : 



1st The IMalomacet exhibit a peculiar spontaneous movement, 

 which is produced by certain locomotive organs. 



2nd. A large number of them have in the middle of the lateral 

 surface an opening about which round corpuscles are situated, which 

 become coloured blue when placed in water containing indigo, just as 

 many of the Polygastic /n/worio. 



3rd. The shells of the IHaiumactir resemble in structure and con- 

 formation thone which are teen in the Mvlltuca and other animals. 



These arguments an met on the other aide by the statement, that 

 us movement is now known not to be specially animal, as 

 of many A Iffir, and their entire fronds an known to be 



actively motile. In the next place the colouring of the interior by 

 indigo also takes place in truly vegetable structures. 



The complex structure of the minute siliceous frustules of the 

 Dialomacett is a fact that has struck many observers. It certainly in 

 without a parallel in the vegetable kingdom. Schleiden in his ' I 

 pies of Scientific Botany,' after giving a minute analysis of the siliceous 

 structure otNaricula riridit (Jig. 6 represents this genus), says, " Sm-h 

 an artificial and complicated structure amongst plants has no explana- 

 tion and is entirely without significance. In all true plants we find 

 the silica present in a very different form, as minute scales or drops, 

 and distributed through the substance of the cell-wall." Again, in 

 another place he says, " This curious structure is wholly without ana- 

 logy in the vegetable kingdom, and cannot be derived from the laws 

 of vegetation with which we are at present acquainted." 



More recently Professor Meneghini has come forward as an advocate 

 of the animal nature of IKatomaceit. In a very lucid and remarkable 



asay, published at Venice in 1845, he says : 

 "If we suppose 



suppose them to be plants, we must admit every frustule, 

 every navicula, to be a cell. We must suppose this cell with walls 

 penetrated by silica, developed within another cell of a different 

 nature, at least in every case where there is a distinct peduncle or 

 investing tube. In this siliceous wall we must recognise a complica- 

 tion certainly unequalled in the vegetable kingdom. It would still 

 remain to be- proved that the eminently nitrogenous internal substance 

 corresponded with the gonimic substance, and that the oil-globules 

 could take the place of starch. The multiplication would be a simple 

 cellular deduplication (sdoppiamento), but it would remain to be 

 proved that it takes place, as in other vegetable cells, either by the 

 formation of two distinct primitive utricles or by the introflection or 

 constriction of the wall itself. Finally, there would still remain 

 unexplained the external motions and the internal changes, and we 

 must prove Ehrenberg's observations on the exterior organs of motion 

 to be false. But, again, admitting their animal nature, much would 

 remain to be investigated, both in their organic structure and their 

 vital functions ; excepting this, so far as we know, we have only one 

 difficulty to overcome, that of the probably ternary non-azotised 

 composition of the external gelatinous substance of the peduncles and 

 inveeting-tubes. But as the presence of nitrogen is not a positive 

 character of animal nature, so the absence of it is not a proof of vege- 

 table. And in order that the objection should really have some 

 weight, it would be well to demonstrate that this substance is isomc- 

 ric with starch. For then, supposing all the arguments in favour of 

 the animal nature of Diatomea were proved by new and more circum- 

 stantial observations, this peculiarity, if it deserve the name of objec- 

 tion, might still be regarded as an important discovery. We should 

 then have in the animal as well as in the vegetable kingdom a ternary 

 substance similar to that forming the basis of the vegetable tissue." 



Of the chemical composition of the Diatomacue little satisfactory has 

 at present been made out Professor Frankland of Manchester, 

 according to the Rev. W. Smith, whose work on the British Diato- 

 maceae is one of the last that has hitherto been published, has found 

 that a large amount of iron exists in the state of a silicate or protoxide 

 in the siliceous frustules, which probably accounts for the brown or 

 yellow colour of these organisms. On the application of tincture of 

 iodine the internal membrane contracts on its contents, and converts 

 these from a golden-yellow to a bright green. On the addition of 

 sulphuric acid they exhibit a deep brown hue. 



The fact which is most relied on to support the vegetable nature 

 of the Diatomacar, by those who advocate this view, does not 

 appear to have been known to Meneghini, and that U the con- 

 jugation of the cells of which they an composed in the same 

 manner as in the Dctmidiae. [DESMIDIE.S.] This discovery was 

 made by Mr. Thwaites, and observed in species of Eanotia (fiy. 1), 

 iu tJ/iit/iemia gibba and . luryida (fg. 19), Fragilaria pcctinalii, and 

 other species. This process takes place as follows: Two indi- 

 viduals closely approximated dehisce in the middle of their long 

 diameter, whenupon four protuberances arise, which meet four simi- 

 lar ones in the opposite frustule. These indicate the future channels 

 by which the endochrome of the two frustules becomes united, as well 

 as the spot where subsequently the double sporangium is developed 

 (fit. 8, 19). From the sporangium the new individuals an develop.,!. 

 This process is precisely analogous to what takes place in the J>et- 

 midiete, so that the frustules of the Diatoms must be regarded as cells 

 of the same individual. " If we duly consider this fact," says Mr. 

 Thwaites, " how much does it exalt the lower tribes of plants in our 

 estimation ! since we may contemplate an individual plant of them 

 not as the single phyton not as the single frond not as the single 

 cell but it may be as the aggregate of thousands of these ; view it 

 occupying as much space and exercising as great an influence in the 

 economy of nature as the largest forest-tree I " 



The mode by which the cells an multiplied amongst the Dia/omaccre 

 appears to be strictly in accordance with what occurs generally in the 

 vegetable kingdom. Thia process is one of self-division. The first 

 step is the fission or division of the internal cell, " probably by the 

 doubling-in of its membranous wall, and consequently the separation 

 of the endochrome, or cell-contents ; the central vesicle or cytoblast 

 also dividing into two parts, which nmove to a little distance from 

 each other; these movements being simultaneous with a retrocession 



