254 T. W. Engelmann on the Infusoria. 



cases be distinguished. In company with these forms were 

 others, belonging evidently to a later phase of development. 

 Thus the large circular nucleus of the embryonic body was sub- 

 divided into two oval segments, which, on the addition of acetic 

 acid, were seen to be enclosed within the common transparent 

 capsule of the embryonic corpuscle (PI. III. fig. 12). One or 

 two similar oval bodies are sometimes found in addition within 

 the parenchyma of the animalcule; and occasionally the nucleus 

 of the Carchesium is not discoverable. It also at times happens 

 that an outgrowth or protuberance appears on the surface of the 

 animalcule, either about its middle or at its anterior part ; but 

 these conical tapering swellings exhibit no distinct aperture, 

 though possibly one may eventually make its appearance. In 

 these prominences an embryonic corpuscle was several times 

 seen ; nevertheless it is doubtful whether the embryos make 

 their exit through them, for Engelmann observed their escape 

 through a fissure near the peristome (fig. 11). The escaped 

 embryo is oval, very small, and furnished with two zones of long- 

 cilia in front, by means of which it swims about in an impetuous 

 manner. Internally it presents a contractile space and a rounded 

 nucleus (fig. 1 1 a) . From these observations Engelmann concludes 

 it to be probable that one or several embryos are derived from the 

 nucleus of the original embryonic corpuscle, which advance in 

 growth at the expense of the matter contained within the cor- 

 puscle, and after a time effect their escape through its surround- 

 ing wall, and lastly through the coats of the parent animal by 

 means of a special foramen. This interpretation coincides with 

 the observations recorded by Claparede respecting the formation 

 of embryos in the Epistylis plicatilis. 



Engelmann has met with but few examples to illustrate the 

 development of embryonic corpuscles from the nucleus of the 

 parent animal. In one instance where there was a large em- 

 bryonic body, the reduced nucleus presented several nuclear 

 structures. In another animal which had no such large cor- 

 puscle, the nucleus was likewise reduced in size, and in contact 

 with it were six small spherical corpuscles having a central 

 vesicle. In a third example, along with a large embryonic body 

 there were five rounded corpuscles, each with a central vesicle, 

 apparently derived from a breaking-up of the nucleus, but dif- 

 fering materially in size among themselves. These were probably 

 produced after the first embryonic corpuscle had developed its 

 embryo, and a series of such corpuscles were prepared for suc- 

 cessive elaboration into embryos. 



In the production of embryonic corpuscles another pheno- 

 menon is presented in the case of Carchesium Aselli, correspond- 

 ing with that seen by Stein in Vorticella nebulifera. This con- 



