SCIENCE- G OS SIP. 



cilia in the members of the Thallophyta which 

 possess them seems to be far more rapid than that 

 occurring in the Protozoa. If one compares the rates 

 of ciliary motion in. say, Vortlcella and Protococcus 

 this will appear obvious, since it is possible to easily 

 observe the movements of the fringe of cilia 

 round the epistome of Vorticella in brighter light 

 than in the case of the cilia of Protocoecus. I am 

 here assuming that good definition in ciliary action 

 depends upon three conditions: i.e. (1) rate of move- 

 ment of the cilia; (2) size of cilium ; and (3) the 

 amount to which the light has to be stopped down 

 by the condenser diaphragm. The latter condition 

 is necessary in order that the edges of any object 

 may be well defined. The ultimate explanation of 

 ciliary action has not yet been arrived at, but one 

 or two theories have been advanced, the most 

 justifiable of which holds that a cilium is hollow, 

 and that the more fluid endoplasm is alternately 

 forced into and drawn back again from the cavity, 

 thus producing the lashing movements. Yet, again, 

 it is probable that the ectoplasm of the cilium is 

 peculiarly irritable, and that under the influence of 

 certain external conditions it is stimulated to con- 

 tract in such a manner as to produce the motions 

 peculiar to it. It may be that these two sup- 

 positions are both partly correct, and that both 

 phenomena occur simultaneously. It is interesting 

 to compare the differentiations of motile structures 

 arising from the ectoplasm as we work up from 

 lower to higher Thallophyta. In the lower forms, 

 such as the plasmodia, we find simple prolongation 

 of the ectoplasm or pseudopodia put out with a 

 very low degree of motility, whereas in such forms 

 as Sphaerella we have delicate structures, or cilia, 

 with a considerable power of rapid motion. 



Photography of Diatoms. — Mr. P. C. Myers 

 ("Journal of Applied Microscopy," [September 1901) 

 gives some very useful hints with respect to the 

 photography of diatoms. He obtains some fine 

 results by using a dry apochromatic objective 

 (3 mm. of -95 N.A.), and as oculars compensating 

 eyepiece No. 8 and projection eyepiece No. 4. 

 These data may be of some use to photo-micro- 

 graphers. The diatoms are mounted preferably 

 in styrax. In the article mentioned there are 

 numerous figures, showing results, magnified some 

 2,500 diameters. Considering the magnification, 

 the definition obtained is remarkably good. 



Structure of the Cocoanut. — For a most 

 excellent article on the " Anatomy of the Fruit of 

 Cocos nucifera " the reader is referred to the 

 October number of the '• American Journal of 

 Science," wherein Mr. A. L. Winton gives a very full 

 account of the macroscopic structure, histology, 

 micro-chemistry, and chemical composition of that 

 most useful article, the cocoanut. The accompany- 

 ing illustrations form a striking point in the 

 article, and even from those alone the student and 

 agricultural expert may learn a good deal. When 

 one considers the difficulty that must have been 

 experienced in obtaining good sections of the 

 various layers — epicarp, mesocarp, and endocarp — 

 of which the cocoanut is composed, and in all of 

 which there are a great number of hard sclerised 

 elements (stone-cells of endocarp), the value of the 

 figures is easily recognised. A peculiarity that 

 will be noticed is the presence of circular or 

 elliptical cells on the surface of the mesocarp 

 fibres, in the walls of which crenated siliceous 

 bodies are found. 





Carychium minimum, Miiller. — One does not 

 often hear much about the variations of a species 

 so small as Caryehiumi minimum. We may be in- 

 clined to think that the smaller species of animals 

 may be so situated in the scheme of biological 

 economy that they are less subject than their 

 larger-grown relatives to those combinations of 

 circumstances which give rise to a marked lack of 

 uniformity among a number of individuals. The 

 following notes are derived mainly from a study 

 of about 240 specimens obtained from the refuse 

 left by a flood in the Thames on Hinksey Marsh, 

 in Berkshire, during the winter of 1898-9. (i) 

 Armature of the Mouth. — Normally the peristome 

 presents three projections into the aperture : one 

 from that part which is reflected over the body- 

 whorl (posterior), one from that part immediately 

 anterior to the termination of the columella 

 (lateral), and one from the free portion (anterior). 

 The posterior one is always the best developed, and 

 may properly be called a denticle ; the other two 

 are blunter and less defined tubercles. During 

 the formation of the peristome they appear in the 

 order posterior, anterior, lateral ; and the latter is 

 often very poorly developed. In some instances it 

 is completely absent, and there is nothing to mark 

 its site. The same is true less frequently of the 

 anterior tubercle. We have not noted a speci- 

 men without the posterior denticle, except where 

 the whole aperture is malformed. In the series, 

 however, all three projections were present in 

 every specimen ; the lateral one was frequently 

 much reduced, but always plainly marked, as were 

 the other two. (ii) Variation in Size. — The length 

 has been carefully measured in 200 specimens 

 with the aid of a microscope and a camera lucida. 

 Measurements were made to - 01 mm., and may 

 probably be taken as correct to 002 mm. The 

 length was taken parallel to the axis of the shell. 

 The results are given grouped to the nearest 

 0-05 mm. to save elaboration of the table : — 



1-70 mm. 



3 



1-95 mm. 



37 



1-75 „ 



7 



2-00 „ 



25 



1-80 „ 



27 



2-05 „ 



17 



1-85 „ 



27 



2-10 „ 



I 



1-90 „ 



. 47 



2 15 „ 



3 



The mean of all the specimens is T919 mm., 

 maximum 2-16 mm., minimum 1-70 mm. I have 

 previously recorded ("Woolhope Transactions," 

 1898-1899, p. 77) that in Herefordshire hardly any 

 variation in length was to be detected ; but the 

 present measurements show that this series varies 

 about as much as any ordinary series of most other 

 British land snails. The following table contrasts 

 these specimens of Carychium with a series of 

 Tachea nemoralis : — 





Within 



Within 



Extreme 



Variation 





10% 



5 % 



Above 



Above 





of mean 



of. mean 



mean 



mean 



C. minimum 



.. 95 5 



66-0 



12-5 



11-4 



T. nemoralis 



. . 94-9 



81-0 



14-3 



12-5 



