1 68 Journal of Comparative Neurology 



commissure and the epiphysis. In no case have we found two 

 epiphyses or any hint that more than one exists. From our study 

 of the epiphysis and the historical matter upon this subject we 

 are of the opinion that more than one true epiphysis will never 

 be found to exist. In favor of the argument for one epiphysis 

 it may be well to note that not a few have been recently misled 

 by Mr. Ritter's article and drawings of Phrynosoma, in which 

 he regarded the epiphysis proper as a second epiphysis, and 

 mistook the much folded plexus for the true epiphysis. See 

 our article, The Epiphysis of Phrynosoma, etc., Jour. Comp. 

 Neur. , June, '93. For discussions of a plurality of epiphyses 

 see Leydig, p. 41 ; His, p. 44; Kupffer, p. 61 ; also his recent 

 work, the schematic cuts of which are reproduced in this paper. 

 In general the epiphysis is tubular in fishes, vesicular in amphi- 

 bians, vesicular and glandular in reptiles, and gladular in mam- 

 mals. There is usually a narrow hollow stalk connecting it to 

 the roof and diverticles are found to proceed from its walls in 

 all types. 



The paraphysis. This portion of the roof is divided into 

 two parts by the velum transversum, and may be termed the 

 pre- or post-paraphysis according as it lies cephalad or caudad 

 of the velum. The post-paraphysis has been variously termed 

 by different authors. The term " Zirbelpolster " was first ap- 

 plied by Edinger and not Burckhardt to whom it has occasion- 

 ally been credited. The post-paraphysis assumes different forms 

 in the various groups and varies more than the epiphysis. In 

 fishes we find either a single layer of cells forming the roof and 

 running over the pallium or a plexiform mass. In amphibians 

 we find a more intricately folded mass, while in reptiles there 

 are two distinct parts, the intricately folded mass and a sac-like 

 evagination which lies, sometimes in close proximity to the epi- 

 physis, giving rise to the term "Zirbelpolster," and sometimes 

 cephalad of the folded mass, as in the black snake (Fig. 1, Plate 

 XVI). In the mammals which we have studied the post-para- 

 physis is not so complex as in the lower groups. The causes 

 for the varied forms found in the paraphysis must, we think be 

 sought for in the mechanics of embryological growth and devel- 



