Ixxviii Journal of Comparative Neurology. 



series of human foetuses. They first appear in the fifth month and 

 have been followed in their development up to birth. Oft-repeated at- 

 tempts have failed to differentiate them in post-foetal life in the human 

 brain, though they are easily demonstrated in those of other mammals. 

 The inability to secure perfectly fresh material is regarded as the cause 

 of the failure and we may regard the forms given at birth as practi- 

 cally those of the adult, since this is true for the pyramidal and neuro- 

 glia cells of the brain. 



In all the foetal stages observed there is a common type for these 

 cells ; a cell body with its long axis at right angles to the brain surface 

 lying in the molecular layer and usually rather more than half way be- 

 tween the layer of pyramidal cells and the brain surface. The pro- 

 cesses are of two kinds, short processes ascending directly from the 

 cell body to the surface where they end in tuberosities, and long tan- 

 gential processes either running directly laterally from the cell or dipping 

 to a deeper level there to turn in a tangential direction perhaps in sev- 

 eral branches. Along the entire length of the tangential processes 

 ascending processes rise to the surface, like the first mentioned pro- 

 cesses. The cell bodies are sparsely distributed, but the fibres are very 

 numerous and make up the major part of this layer. The author there- 

 fore suggests that this layer be named the layer of Cajal's cells in place 

 of the now no longer applicable " molecular layer." 



c. J. H. 



The Sensory Organs of the Fins of Gurnards.* 



The study of the central nervous system was purely incidental but 

 the figures illustrate clearly the large excrescences to the dorsal cord 

 due to the specialized development of the first three spinal nerves. 

 We may add that very important assistance to a proper understanding 

 of the brain segments and their homologies may be expected from a 

 comparative study of these protuberances which, like the lobi vagi, 

 occur sporadically among fishes. We already know that the cerebral 

 hemispheres seem to have been called into being primarily by the emer- 

 gence of one of the senses (smell) and are prepared to understand that 

 anything which accelerates the development of a sensory segment in 

 the cord may produce a like protuberance anywhere in the myelon. 

 The nature of the connections and modifications resulting may well 

 give us an important clue to the apprehension of the morphological 

 significance of the brain segments. Of these matters the paper gives 



1 Morrill, A. D. The Pectoral Appendages of Prionotus and their Inner- 

 vation. Journ. Mophology, XI, i. 



