INFUSORIAL ANIMArCULES. 45 



examples, even more ; but, in the latter case, the animalcule is 

 usually in the act of self-division. When more than one vesicle is 

 present, there seems no necessary correspondence between the systole 

 and diastole of each. 



With respect to the number of these sacs, in particular species, 

 there is much difference of opinion (only to be reconciled bj- the 

 observations of others, and by accurate deiinitions) between Ehrenberg 

 with his disciple Eckhard, and Siebold. The last-named wiiter 

 affirms that the dctcnuination of these vesicles, by Ehrenberg, is 

 altogether arbitrary, one or two being called sperm sacs, and others, 

 just like them, stomachs, as, for instance, in Amphileptus Meleagris, 

 and in a A. LonglcolUs. Ehrenberg's views are, however, supported 

 by Eckhard, who finds some dilFerence in the character of the con- 

 tractions in the different sacs, and affirms that he is unable to verify 

 the existence of the lateral abdominal contractile vesicles in Stentor in 

 the elongated one in Spirostomum mnhiguum, described by Siebold. 

 Yerglcichenden Anatomic der Wirbellosen Thiere Vol. I. In Para- 

 mecium, the conti-actile vesicle is large, and has from 6 to 8 radiating 

 prolongations, which are filled when the central reservoir empties 

 itself, and become invisible, when its diastole occurs. 



Erom this, and other like phenomena, presented by these contractile 

 vesicles, Siebold, and others, attribute a cardiac nature to them, sup- 

 posing that upon their diastole, they become filled with nutritious 

 fluid, derived from the parenchyma, thi'ough the insterstices of which 

 it is again forced, on the occurrence of the systole, and stagnation, 

 thus avoided. 



The hypothesis of their generative ftmction, Siebold declares per- 

 fectly gratuitous; that an incessant projection of seminal fluid from these 

 vesicles, involves, in itself, a supposition opposed to all analogy ; and 

 further, that the purpose of the nucleus as a testes, and even the ex- 

 istence of recipient ova in the parenchyma, are more than doubtful. 



A process of respiration, — a renovation of the fluid in the paren- 

 chyma, and around the animalcule, is no doubt canied on by the 

 external surface, especially by means of the cUia ; and, very probably, 

 also by the series of contractile spaces, often seen immediately sub- 

 jacent to the integument, as well as by the constantly recurring 

 contraction of the supposed cardiac vesicles. The spaces met with 



