348 JOHN WARREN 



The paraphysis was first recognized as a distinct organ by Se- 

 lenka (86) in the opossum. Kupffer and Burckhardt traced its 

 history in cyclostomes. In Petromyzon and Ammocoetes it 

 forms rather a small sack-like outgrowth, Kupffer (57) figs. 47 

 and 57, Burckhardt (12). Minot has traced it in elasmobranchs, 

 especially in Acanthias (71), figs. 6-10, where it is a very simple 

 evagination. Kupffer found it in ganoids and described it in 

 Accipenser as a small vesicle, slightly folded at first, fig. 117, which 

 later gives off tubules. Hill, Eycleshymer and Davis have ob- 

 served it in Amia. It has been described by Terry (102) in 

 Opsanus and by Burckhardt in other teleosts where it is lacking 

 or else appears in a very rudimentary condition. In Protopterus, 

 Burckhardt (13), pi. 8, records a wide sack-like paraphysis the 

 walls of which are much folded. In amphibia it reaches the 

 highest degree of development becoming a large complicated 

 glandular organ, with a central lumen from which a very compli- 

 cated set of anastomosing tubules are given off. It extends for- 

 ward above and between the hemispheres and has a well marked 

 sinusoidal type of circulation, Warren (97) figs. 17 and 20. Osborn 

 has shown it in Siredon, Necturus, Proteus and Siren, Burck- 

 hardt in Ichthyophis and Triton. In all these forms it closely 

 resembles the condition seen in Necturus as is the case also with 

 the paraphysis of Rana, Minot; Amblystoma, Eycleshymer; and 

 Diemyctylus, Mrs. Gage. 



Francotte made the earliest observations on the paraphysis in 

 the lacertilia. At first he confused it with choroid plexus but 

 later recognized it as a distinct organ. In his thesis (28) he pre- 

 sented a series of photographs of embryos of Anguis fragilis. In 

 his fig. 8 the paraphysis, velum, post velar arch and epiphysis 

 are similar to my models of Lacerta muralis, 5 mm., fig. 9, while 

 his figs. 12 and 13 are sections of the paraphysis of an embryo 

 rather older which corresponds to my fig. 10. His fig. 15 would 

 correspond to that of Lacerta viridis of 37 mm., fig. 12. Fran- 

 cotte does not give, however, the size of his embryos. His fig. 31, 

 a lizard embryo, is also about this stage, though there is no plexus 

 in the diencephalon. His figs. 27 and 28 show the relations in 



