96 ORGANIZATION OF THE INFUSORIA. 



by Biitschli that the endoplast of each individual divides, during conjuga- 

 tion, into four fragments, which, becoming rounded into a form corresponding 

 with the so-called "ovules" of Balbiani, are cast out of the body as "waste 

 matter." The same destiny is likewise attributed by him to one out of the 

 four fragments into which the endoplastule becomes divided two remaining 

 to represent the normal complement of these structures, and the residual 

 one assuming first a more considerable volume and transparent aspect, and 

 ultimately redividing and constituting the two new nuclei or endoplasts. 

 The endoplastules in all cases preceding subdivision assumed a fusiform 

 shape and striated character, but in no instance was an interchange of these 

 structures between two conjugated animalcules witnessed, as was affirmed 

 to take place by Balbiani. Qualitatively, the endoplastules of the Infusoria 

 are regarded by Biitschli as differing in no way from the endoplasts, and 

 into which latter, in accordance with his observations, they not unfrequently 

 develop. The idea that embryos are developed independently from the 

 endoplast is entirely rejected by this author, the significance attached by 

 him to this structure being simply that of the nucleus of an ordinary animal 

 or vegetable cell. The only reproductive faculty conceded to the Infusoria 

 by Butschli is that of division or gemmation, the conjugative act being 

 associated by him only with the conference of renewed power or vital 

 energy for the continuation of the dividing process. The superficial 

 analogy existing between the complete conjugative process, as exhibited in 

 the genus Vorticella, with the union of the ovum and spermatozoon of the 

 higher animals, is accorded by this author, but hermaphroditism or sexual 

 differentiation, as a constant and essential feature of the representatives of 

 this organic group, is entirely denied. The unicellular nature of the 

 Infusoria is necessarily maintained, in the most thoroughgoing and forcible 

 interpretation of the term, in connection with Biitschli's foregoing exposition 

 of the reproductive features. 



Engelmann's latest independent investigations in this direction, while 

 resulting contrary to his earlier researches in an entire acquiescence with 

 the views of Butschli, so far as the reconstructive properties of the endoplast 

 and the total rejection of the embryonic theory are concerned, exhibit certain 

 points of difference. Thus, although the nucleus or endoplast is regarded 

 by him in most instances as the equivalent simply of the nucleus of the 

 histologic cell, this same structure is in certain cases, such as Stylonycliia 

 and Euplotes, interpreted as representing a female element, while the 

 accompanying nucleoli or endoplastules are further stated to be exchanged 

 between two conjugating individuals, and held to exert a possible fecun- 

 dating influence in the building up of the new nucleus. In the case of 

 Vorticella, where conjugation or zygosis is complete, the usually smaller 

 detached zooid, whether derived by fission or gemmation, that encounters 

 and buries itself in the substance of a larger sessile individual, is regarded 

 as a male zooid, and the latter sessile one as the female ; in this sense the 

 Vorticellidae and other types exhibiting similar phenomena are deemed to 



