47 6 COMPARATIVE ANATOMY AND PHYSIOLOGY. 



protoplasm, has become motile, and been converted 

 into a pseudofilaria. 



The statement that a kind of sexual reproduction is 

 observable among the Infusoria has, on account of 

 the detailed characters of the reported observations, 

 obtained considerable vogue. Put shortly, the account 

 comes to this ; the substance of the nucleolus becomes 

 converted into a number of curved rods, which repre- 

 sent the male element, while the nucleus breaks up 

 into small spherical bodies, which have been compared 

 to ovules. The resulting young are said to be at 

 first provided with knobbed tentacles and suckers 

 (acinetiform embryos), and to become gradually con- 

 verted into ciliate infusoria. Observations undertaken 

 with the express view of examining into these results, 

 have done anything but confirm them, for they have 

 resulted in the conviction that the rod-shaped bodies 

 of Balbiani are nothing but bacterioid parasites 

 (Vibrios), and that the so-called embryos are also para- 

 sites ; these last, indeed, have, on direct observation, 

 been seen to enter the body of one after escaping from 

 another Infusorian. What really does happen appears 

 to be this ; two individuals (of Paramoecium) conjugate, 

 and remain united for a day or longer ; the only result 

 of this conjugation is that the nucleus becomes more 

 finely granular, while the nucleolus breaks up into 

 four oval capsules. Of these, two in each individual 

 disappear, while the other two grow till they reach 

 two-thirds the size of the original nucleus, which they 

 then resemble in appearance ; one of these remains 

 as a nucleolus, and the other appears to fuse with the 

 primitive nucleus. 



The process, then, instead of being in any way sex- 

 ual, falls rather under the head of rejuvenescence ; 

 the protoplasm, in other words, seems to undergo a 

 kind of re-arrangement in much the same way as, in 

 the political world, cabinets sometimes do. 



