POLYGASTRIA. 



a single cubic line, to eight thousand millions, 

 and a cubic inch of such water containing 

 1728 cubic lines, will be peopled with thirteen 

 billions eight hundred and twenty-four millions 

 of these living and active beings ! ! ! 



It has been possible to detect, even in these 

 smallest of nature's works, an apparatus that 

 seems to perform the functions of an instrument 

 of progression. This consists in one or some- 

 times two filaments of extreme tenuity, which 

 resemble somewhat the tail of a tadpole ; here, 

 however, the organ performs the functions of a 

 proboscis, being appended to that part of the 

 body which advances first in swimming. The 

 shape of the Monads is not always globose, 

 but sometimes egg-shaped, pear-shaped, elon- 

 gated, or fusiform. In Monas tingens we have 



Fie. 1. 



1. Uvella glaucoma. 2. Polytoma itvella. 3. Mi- 

 croylena monadina. 4. Bodo socialls. 5. Lagenella 

 euchlora. 6. The same crushed, showing its shell. 

 7. Gonium perforate. 8. Gonium pectorale, breaking 

 up into its component animalcules. 9. Eudorina. 

 10. One of the animalcules comprising Eudorina 

 detached. 11, 12, 13. Developement of Volvox. 



an example of the last form, and also of the 

 manner in which they are sometimes found 

 associated by their tails into beautiful groups, 

 their double proboscides being all protruded 

 externally. 



This faculty of clustering together is still 

 better exemplified in the genus Uvella, (1, 

 Jig. 1,) which somewhat resembles a trans- 

 parent mulberry rolling itself about at will, 

 whence the name " grape monad," which these 

 animalcules bear. In Polytoma (2, jig. 1) 

 this clustered appearance is due to the fact that 

 the original animalcule is continually dividing 

 into a greater and still greater number, which, 

 at last breaking loose from each other, become 

 solitary and independent. 



Some animalcules of this family, as Chilo- 

 tnonas destruens, live in the interior of dead 

 Rotifers and other minute beings, in which 

 locality they seem to revel luxuriously; whilst 

 others, as Bodo, (4, Jig. 1,) are met with in 

 the intestinal canal of many living animals,* 

 from the fly and the earth-worm up to fishes 

 and even men. One species (B. ranarum) 

 seems particularly partial to the intestines of 

 Frogs, in the contents of which it is usually 

 found. Many species of this genus are fur- 

 nished with long tails, by the aid of which 



* Ehrenbcrg, Infusionsthicrchen. 



they are bound together in bunches of very 

 beautiful appearance, as represented in the 

 figure. 



In the Cryptomonads, (5, fig. 1,) which 

 seem to be merely Monads invested with a 

 shell, the proboscis is of a similar character ; 

 but these animalcules are never found asso- 

 ciated in bunches. 



Perhaps few more beautiful objects exist in 

 nature than the next group of animalcules 

 belonging to the Monadine type. These are 

 the Volvocinidae, embracing several genera 

 composed of numerous Monads, associated 

 together and connected by a common envelope, 

 which constitutes a kind of compound poly- 

 pary or monadary, as it has been recently 

 called, through which the proboscides of the 

 component Monads are exserted. 



In Gonium, (7, 8, Jig. 1,) one of the 

 simplest forms belonging to this family, the 

 common body resembles a minute square- 

 shaped flattened tablet, so transparent as to be 

 detected with great difficulty, in which the 

 green Monads are set like the gems in the 

 breastplate of the Jewish high-priest, from 

 which circumstance one species, G. pectorale, 

 has been named. 



The organisation of Gonium pectorale, as 

 far as it has been made out, seems to be as 

 follows : The mantle or proper covering of 

 each individual animalcule, which can only be 

 properly examined after the division of the 

 little tablet, is neither four-cornered nor table- 

 like, but pretty nearly round, and in the form 

 of a lucerna, which the animalcules can quit 

 and renew again at intervals. The table-like 

 investment of the compound body is produced 

 by regularly repeated spontaneous fissure in 

 the longitudinal, but not in the transverse di- 

 rection, which is in fact only an imperfect 

 division into single tablets. In a little tablet of 

 this kind all the animalcules of which it is 

 composed appear to be connected to each other 

 by riband-like prolongations. 



It is only in Gonium pectorale that locomo- 

 tive organs have been satisfactorily detected, 

 presenting themselves under the usual form of 

 two thread-like proboscides, appended to the 

 mouth of each individual Monad entering into 

 its composition. These are seen to be in con- 

 stant motion, so as to have the appearance of 

 cilia.. 



Each individual animalcule inclosed in the 

 common envelope of the compound being ap- 

 pears, moreover, to possess a distinct nutritive 

 apparatus, consisting of transparent vesicles 

 visible among the green matter that fills its 

 interior ;. but these have not yet been observed 

 to fill themselves with colouring matter. Eh- 

 renberg likewise supposes that each of the 

 component animalcules of the Gonium contains 

 the essential parts of a double sexual system, 

 regarding the green-coloured particles in the 

 body as eggs, and an opaque spot and con- 

 tractile bladder, which is occasionally discern- 

 ible, as the male apparatus; but these parts 

 will be more particularly described hereafter. 



The most beautiful animalcules belonging 

 to the Volvocinidae are the Volvuces, from which 



