INFUSORIA. 
Prot. 3 
sidered by Engelmann as representing, to a certain degree, the male 
element, since they conjugate (are completely fused) with the 
larger sessile (“ female ”) individuals. During and before this fusion 
the “ nuclei ” of both individuals undergo a division, which results 
in the formation and mixing up of a great number of small nuclear 
globules ; these, however, have no connection with any process of 
multiplication or propagation ; subsequently they are reunited into 
larger and larger corpuscles until the single nucleus is thus entirely 
reconstructed. The Vorticella resulting from the “ zygosis ” is thus re- 
organized, and capable of resuming the process of fission ; the “ nucleus 
is neither egg, ovarium, nor sporangium, it is only the true cell-nucleus 
of the monocellular animalcule. In other Infusoria^ the whole animal is also 
reconstructed after the incomplete conjugation, which is followed by the 
separation of the individuals ; but here also the conjugation provokes a 
disintegration and afterwards reconstruction of the nuclei, after which they 
are capable of resuming their propagation by division. These Infusoria 
{Euplotes^ Stylonichia, &c.) are considered by Engelmann as hermaphroditic, 
because of the differentiation of the nucleus into a true (female ?) nucleus 
and a (male ?) “ nucleolus.” During the transformation of the nuclei, the 
“ nucleoli ” first increase, then divide into two, four, and eight, the con- 
tents whereof assume a fibrillate structure ; these “ seminal vesicles,” or the 
“ nucleoli ’ themselves, are exchanged between the conjugating individuals, 
and probably exercise a fecundating influence upon the reconstruction of 
the nuclear fragments into the new nucleus. In Stentor, Trachelius, &c., 
this' hermaphrodite state of the animal cell is only transient [?] ; in 
Stylonichia a complete zygosis (“ copulation ”) occasionally takes place, 
accompanied by fusion of the respective nuclei and nucleoli, but not fol- 
lowed by any of the changes taking place after the ordinary incomplete 
conjugation. The so-termed “embryos” of different Infusoria — also 
when developed from “ embryonal globules,” which are in this instance 
encysted intruders ; in others they are either excrementitious bodies or the 
corpuscles resulting from the disintegration of the “ nuclei ” — are always 
parasites, commonly Acinetina ; the ciliated parasites (pseudembryOs) 
of Vorticella are termed Endosphcera (g. n.). The “ embryonal theory,” 
therefore, is entirely rejected, after a profound criticism, though some of 
Engelmann’s older observations have been regarded by Stein as one of 
its most solid pillars. — These results are mainly confirmed by the de- 
tailed researches of Butschli (1), made upon a considerable number of 
Infusoria {Paramcecium, Cyrtostomum, Colpidium, Glaucoma, Blepharisma, 
Chilodon, Condylostoma, Bursaria, Stylonichia, Euplotes, Vorticella, Epi- 
stylis,&c.) ; as they are made quite independently of those of Engelmann, 
some of the most important and most intricate questions in the history 
of Infusoria may now be regarded as definitively settled. Butschli also 
considers the conjugation of the Vorticellina as analogous with the 
union of the spermatozoon with the egg, but he insists less strongly upon 
the hermaphrodite sexuality of other Infusoria ; the only reproduction 
known in these Protozoa is division (or gemmation). When the divisi- 
bility of the individuals, after repeated fissions, begins to slacken, and the 
individuals themselves are becoming very small, the vital energy is re- 
