Literary Notices. xxxi 



cells migrate toward the periphery the natural polarity asserts itself 

 and the cells become elongated tangentially to the brain surface and 

 typically bipolar or else stomach-shaped, the cellipetal fibres and the 

 cellifugal fibres joining the cells at right angles to each other. 



The fibre tracts are partly myelinic and partly amyelinic, the 

 latter being confined to the prosencephalon and the most of the dien- 

 cephalon, and represented by the precommissure, callosum, supracom- 

 missure, Meynert's bundle and a portion of the peduncular tracts. 



We quote the first paragraph of the authors summary. " The 

 preservation of so many embryological features both in the morphol- 

 ogy and histology of the neuraxis of the Desmognathus is quite re- 

 markable. Throughout the whole length of the tube there may be 

 recognized the homology of the three layers as described by His. In 

 the early embryo the ental layer is composed of epithelium, or en- 

 dyma; the middle or mantle layer consists of the cinerea, and the 

 ectal layer of alba. The nerve cells appear to be scarcely more than 

 fairly well developed neuroblasts. The regeneration of lost parts in 

 the Urodeles is well known, and this phenomenon may be more or 

 less dependent upon the embryonic condition of the elements of the 

 neuraxis and their power of rapid growth utilized in this direction." 

 This goes far to substantiate the view previously expressed in the col- 

 umns of this Journal that the Urodela are permanent larva, so far as 

 the essential points of cerebral structure are concerned. While this 

 makes it necessary to use some caution in deducing phylogenetic con- 

 siderations, it by no means minimizes their importance to phylogeny. 



The other features in Professor Fish's paper we cannot dwell 

 upon, but commend the whole as a welcome contribution to a difficult 

 subject. c. J. H. 



The Paraphysis.^ 



In a brief paper Studnicka reviews the current morphological 

 teachings about the paraphysis and endeavors to show that in Petro- 

 myzon the anterior parietal organ has nothing to do with the paraphysis. 

 The anterior parietal and the pineal may be regarded as serially ho- 

 mologous sensory organs, but the paraphysis has no such function, 

 nor is there evidence that it has ever had such. The author reiterates 

 the belief that the anterior organ is homologous with the parietal eye 

 of saurians. The paraphysis in Petromyzon lies well forward of the 



'Studnicka, F. K. Zur Anatomic der sog. Paraphyse des Wirbelthier- 

 gehirns. Siizb, k.bohm. Ges, der Wissenschaflett, Prag, 1895. 



