XXXll PROCEEDINGS OE THE *" 



many other lower animals. He is not, however, disposed to make too 

 broad a generaUzation and to insist on the presence of an alimentary 

 canal distinct from a body-cavity in all the other Infusoria. Here, 

 however, he falls in with the views of Claparede and Lachmann and 

 of Greeff, and maintains that as a rule the digestive and body-cavity 

 in the Infusoria are confounded into a single gastrovascular system. 



Independently, however, of the untenableness of the conception 

 of a united digestive and body-cavity, it does not appear to me that 

 Balbiani makes out any case against the unicellularity of the Infu- 

 soria. He admits that, except in the pharyngeal and anal portion, 

 there is no evidence of a differentiated wall in his so-called digestive 

 canal ; and even though it be conceded that the middle portion of 

 this canal constitutes a permanent cavity in the parenchyma, it 

 would not differ essentially from other lacunae permanently present in 

 the protoplasm of many undoubtedly unicellular organisms. It has 

 been already remarked that a communication between these lacunae 

 and the external medium is parallelled in many simple cells ; and these 

 external communications in Didinitim present no feature essentially 

 different. 



The pharynx appears to be bounded by an inflection of the cor- 

 tical layer ; and I believe we may regard the rod-like corpuscles here 

 present as a peculiar modification of the trichocysts, which, in many 

 other Infusoria, are developed in the cortical layer of the body. The 

 projectile tongue-like organ is one of the most remarkable features 

 of Diclinium ; we must know more, however, than Balbiani has told 

 us of it before we can decide on its real import. It is not improbably 

 a pseudopodial extension of the protoplasm. 



Balbiani has followed the Bidinium through the process of trans- 

 verse fission. This is preceded by the formation of two new wreaths 

 of cilia, between which the constriction and division take place, 

 each half, previously to actual separation, developing within it such 

 parts as it had lost in the act of division. The only part which in 

 this act becomes divided between the two resulting animals is the 

 nucleus. The so-called nucleolus was not seen by Balbiani ; and 

 though he observed two individuals in conjugation by their opposed 

 oral surfaces, he never witnessed any thing like the formation of eggs 

 or embryos. 



I believe I have now laid before you the principal additions which 

 during the last few years have been made to our knowledge of the In- 

 fusoria ; but though it will be seen that the labourers in the special 

 fields of microscopical research to which I have confined this address 



