356 ABSTRACTS OF PAPERS. [VOL. II. 



If the oblique cut makes with the colonial axis an angle 

 larger than forty-five degrees, there is no displacement of the 

 lateral polyp, the extirpated axial polyp regenerating as though 

 it alone had been removed by a transverse cut. 



5. When a lateral group of polyps is removed by a longi- 

 tudinal cut, it regenerates a new peduncle approximately at a 

 right angle to the cut surface, and approximately in the axis 

 of the chief lateral polyp of the group. The future of such 

 pieces is unknown. This is a case of heteromorphosis. 



XXI. SOME POINTS IN THE BRAIN OF 

 LOWER VERTEBRATES. 



J. B. JOHNSTON. 



THE central olfactory apparatus of Petromyzon presents, in 

 all important features, an extraordinary resemblance to that 

 of Acipenser. In Petromyzon, on account of the great buccal 

 apparatus, there has occurred a sort of telescoping of the olfac- 

 tory lobes and areas upon the striatum and thalamus as fixed 

 points. The so-called cortex, described by Friedrich Mayer, 

 is nothing else than the epistriatum. 



The cells of the olfactory lobe present more primitive char- 

 acters in Petromyzon than in Acipenser. The mitral cells are 

 only slightly differentiated, while the stellate and other cells 

 are very numerous and send their neurites, along with those 

 of the mitral cells, to the olfactory nuclei of the fore-brain. 

 Similar categories of cells have been described in Amphibia 

 (P. R. Cajal) and reptiles (Edinger's " Lobuscortex "), although 

 differently interpreted. The numerous, slightly differentiated 

 cells in the olfactory lobe of Petromyzon and Acipenser 

 represent the material from which the highly differentiated 

 elements of the olfactory lobe of higher vertebrates have 

 been developed. 



Several authors have pointed out the close connection 

 between the cerebellum and acusticum in fishes. The study 

 of the minute structure shows that the cerebellum is derived 



