98 ORGANIZA TION OF THE INFUSORIA. 



unimportant minority. Undoubted evidence of the production of embryos 

 through the breaking up of the substance of the endoplast is afforded, in 

 addition to the instances already cited, by Haeckel, in his account and 

 illustrations of the pelagic form Codonella campanella, and by Balbiani, in 

 connection with his most recent investigations of the Miillerian type 

 Didinium nasutum. In the genus Euglena and its allies, the production of 

 embryos through the increment in size and splitting up of the substance of 

 the endoplast has been amply demonstrated by Stein and Carter, and 

 is confirmed also by the observations of the present author. As a last 

 illustration of this production of germs or embryos through the subdivision 

 of the endoplastic element, may be cited Professor Allman's account of 

 the development of a species of Epistylis, communicated to the meeting of 

 the British Association, held at Brighton in the year 1875. In this case 

 individuals possessing a normal development of the ordinary band-like 

 endoplast were observed to undergo encystment, the enclosing membrane 

 becoming after the lapse of a few days so opaque as to preclude a clear 

 view of its contents. Upon breaking the capsule open, however, it was 

 found that the endoplast had increased prodigiously at the expense of 

 the surrounding plasma, presenting the aspect of a long and much con- 

 voluted cord, while in still more advanced phases this cord-like endoplast 

 had separated into a number of ciliated and free-swimming germs whose 

 contour, as in the case of Didinium nasutum, most closely resembled the 

 adult form of Trichodina (Halteria) grandinella. Reproductive phenomena, 

 closely corresponding with those just described, have been recently reported 

 by Everts of Vorticella nebulifera. 



Before finally dismissing the subject of the production of embryos from 

 the substance of the endoplast, a protest must undoubtedly be lodged 

 against Biitschli's assertion that the fragments into which it becomes 

 separated during or after conjugation, are merely cast out of the body as 

 waste matter. Such an unprofitable destiny is not usually found associated 

 with so essential a structure, and in place of the purely negative evidence 

 adduced, it is equally probable, and far more logical, to presume that 

 these detached fragments represent germs which ultimately develop to 

 the parent forms, as in the case of the endoplastic fragments of Stentor, 

 Vorticella, Euglena, and other types already alluded to. Whether or 

 not the conjugation or fusion of two individual animalcules exerts a direct 

 influence upon the sporular or gemmiparous reproductive phases, in addition 

 to the more ordinary binary segmental one, is as yet scarcely determ in- 

 able, though that in the first-named case it commonly, if not more usually, 

 precedes spore-production is made evident through the investigations of 

 Messrs. Dallinger and Drysdale, added to those of the present author, in 

 connection with a considerable number of Flagellata. 



With respect to the actual act of conjugation, fusion, or zygosis, as it is 

 variously denominated, it is worthy of remark that where such conjugation 

 is complete and permanent, as in the family of the Vorticellidae, and so far 



