GENETIC REPRODUCTION. 95 



capsules were respectively exchanged, the so-called ovules in each ani- 

 malcule being thus mutually fertilized on a plan corresponding with that 

 exhibited by the Helicidae and other monoecious Gasteropoda. These 

 phenomena of fusion or genetic union, first reported of Paramecium, were 

 recorded by the same observer as occurring in a variety of animalcules, 

 and were soon, so far as the external circumstances were concerned, found 

 to obtain very generally, but under varied conditions, the union being 

 sometimes transitory and in others permanent, throughout the whole 

 infusorial class. Among the authorities who, after devoting themselves 

 specially to the investigation of this organic group, have arrived at con- 

 clusions confirming the discoveries of Balbiani, and have relegated to the 

 nucleus and nucleolus the same respective genetic functions, may be men- 

 tioned the names of Kolliker, Stein, Claparede, and Lachmann, and, in a 

 slightly modified manner, also Mr. Carter. This last-named author, how- 

 ever, previous to the discoveries of Balbiani,* attributed the production of 

 spermatic elements to the nucleus, and that of germs or ovules to the 

 general body-substance. 



An examination may now be made of those recent discoveries of Engel- 

 mann and Biitschli which have resulted in the introduction of an entirely 

 new train of thought respecting the reproductive properties of the Infu- 

 soria. After a prolonged and independent research, these two authors 

 have, while admitting the conjugative process, been compelled to reject in 

 toto Balbiani's interpretation assigning to the endoplast and endoplastule 

 respectively the functions of an ovary and testis. The characteristic 

 striated aspect exhibited by the endoplastule during conjugation is de- 

 clared by them to be in no way connected with the production of spermatic 

 elements, but to represent the normal aspect of both this structure and 

 the nucleolus of the ordinary tissue-cell prior to the act of subdivision. 

 Nuclei, in both animal and vegetable cells, are further maintained by them, 

 and confirmed by the observations of Hertwig and Strassburger, to fre- 

 quently exhibit a similar striated appearance and general likeness to the 

 so-called " seminal capsules " of the Infusoria. Briefly epitomized, the 

 general conclusions arrived at by Biitschli with reference to the conjugative 

 process of the Infusoria are as follows : During such process the original 

 nucleus or endoplast in both animalcules breaks up into a number of 

 fragmentary portions, and becomes lost among the endoplasm or general 

 body-sarcode. By-and-by an entirely new endoplast is constructed through 

 the gradual assemblage and union with each other of fragmentary particles 

 having a similar general derivation, this newly found endoplast being single 

 and common to the two in such instances as Vorticella, where conjugation 

 or fusion is complete and permanent, while two or more, according to the 

 normal number, are reproduced where such conjugation is, as in Paramecium, 

 partial and transient. In the case of Stylonychia mytilus it is further affirmed 



* H. J. Carter, " Notes on the Freshwater Infusoria of Bombay," ' Ann. and Mag. Nat. Hist.,' 

 Ser. ii. Nos. civ. and cv. 1856. 



