GREGARINIDA, RHIZOPODA, SPONG1DA, AND INFUSORIA. 19 



gemmation which many of the group exhibit are well known ; 

 but within the last few years the investigations of Midler, 

 Balbiani, Stein, and others, have shown that these minute 

 creatures possess a true process of sexual multiplication, and 

 that the sexual organs are those which have been denominated 

 ' nucleus " and " nucleolus." The nucleus is the true ovary — 

 the nucleolus, the testis, in Paramoecium. At particular times, 

 the latter increases very much in size, and its substance is 

 broken up into rod -like bodies, which represent spermatozoa. 

 Two Infusoria, in this condition, become conjoined, and the 

 nucleolus (now converted into a spermatic capsule) of each passes 

 into the body of the other. The spermatic filaments are said to 

 enter the nucleus, which then enlarges, and either divides into, 

 or gives off, a number of rounded germs, which become oval 

 ciliated bodies provided with long processes. These make their 

 way out of the body, and, it is believed, are metamorphosed 

 directly into young Paramoecia. But, perhaps, further informa- 

 tion is required before we can be quite certain on this point. 



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