Dr. C. F. J. Lachmann on the Organization of Infusoria. 239 



he had overlooked them ; whether^ instead of several globules, 

 only one very large one, entirely filling the mother-vesicle, had 

 been produced ; or whether two diflFerent modes of development 

 actually occur in this case. This is the only mode of reproduc- 

 tion of the Infusoria which has hitherto been observed in encysted 

 animals alone ; but some observations made by E. Claparede and 

 myself upon an undescribed vaginicolous Infusorium, indicate 

 that ency station is not a necessary condition even for this mode 

 of propagation. The internal formation of embryos in Chilodon 

 has been observed by Stein, especially in encysted animals, but 

 nevertheless, according to him, it also occurs in free animals. 

 Fissation is very frequent in the interior of cysts ; many Infu- 

 soria appear to undergo fissation more frequently in cysts than 

 when swimming freely ; so that it may appear probable that the 

 cyst serves as a protection for the animal when dividing, but it 

 is certainly not necessary, as we are acquainted with no example 

 of an Infusorium which always encysts itself for the purpose of 

 fissation. Thus the principal, if not the only object of encysta- 

 tion appears to be protection against unfavourable external cir- 

 cumstances. 



With regard to the peculiar process of copulation or zygosis 

 of the Infusoria, as its object is still entirely unknown, I shall 

 only state, that, except in the Diatomacese and Desmidiacese, the 

 position of which is still doubtful, it has hitherto been observed 

 particularly in Actinophrys and Acinetina*. According to an 

 oral statement, E. Claparede has also seen Vorticellince (especially 

 V. microstoma) in zygosis ; and I have twice met with double 

 animals of Carchesium, still sitting upon a double stalk and con- 

 stantly becoming more amalgamated, so that the cavities of both 

 the fused animals communicated, and the morsel which was 

 passed from the pharynx of one animal usually ascended in 

 the cavity of the other up to the lower surface of its ciliary 

 disk. The rotatory organs remained separate, and after the 

 lapse of some time, the double animal cast itself loose from the 

 stems, and swam about for more than twenty-four hours by 

 means of a circlet of cilia, which was produced around the 

 rounded hinder extremity formed by the coalescence of the two 

 posterior extremities of the individual animals. 



If we now once more sum up the results of the preceding- 

 statements, we find, — that the Infusoria cannot be regarded as 

 unicellular animals, although they have not a polygastric diges- 

 tive apparatus, but possess a large alimentary cavity furnished 

 with an anus, and into which an oesophagus usually hangs down 

 from the mouth; that a vascular system, of which the central 



* I have seen several in conjugation ; amongst others, even the Acineta 



