712 SUMMARY Of CURRENT RESEARCHES RELATING TO 



the young male differentiates in the adult into anterior paired Leydig's 

 glands and a posterior unpaired kidney. The glands of Leydig do not 

 function as a renal organ, as is shown by their minute structure and by 

 the contents of their ducts. From the condition of the spermatozoa at 

 intervals in the long coiled sperm-ducts (Leydig's ducts) it may be 

 inferred that the function of the glands of Leydig is the secreting of a 

 fluid which nourishes the spermatozoa. 



The sexual kidney or " Geschlechtsniere " is represented in the adult 

 male only by the rete testis, efferent ducts and longitudinal collecting 

 duct. Moreover, an epididymis, as usually defined, is absent. The 

 development of the glands of Leydig is accompanied by changes in the 

 sperm-ducts and the formation of highly complex sperm- vesicles. The 

 anterior region of the urinary organs undergoes retrogressive develop- 

 ment, as is shown by a comparison of this structure in immature and 

 adult females. 



There is a distinct urogenital sinus in the young female which does 

 not persist in the adult. The application of the term " receptaculum 

 seminis " to the digitiform gland found ventral to the urinary bladder 

 is erroneous, and this structure must for the present be regarded a-- a 

 female accessory genital gland of obscure function. 



Skeleton of Frilled Shark.*— T. Goodey gives an account of the 

 skull, arches, vertebral column, girdles, fins, and mixipterygia of 

 Chlamydoselaclms anguineus. The following are a few of the most 

 important points dealt with in the paper : — 



The membranous labyrinth is described and figured for the first 

 time. It is of the usual Selachian type, resembling rather closely that 

 of Hexanchus griseus. 



In regard to the formation of the centra, there are at the anterior 

 end of the vertebral column well-developed, calcified, cyclospondylic 

 centra ; there are slight constrictions of the notochord in the trunk 

 region, best seen in horizontal longitudinal section, not calcified — the 

 lowest stage in the development of centra ; in the main caudal region, 

 calcified cyclospondylic centra occur, of two sizes corresponding with 

 the doubling in the number of arcualia, which here, more than else- 

 where in the vertebral column, grow round the notochord and greatly 

 strengthen the centra. 



The terminal caudal region is heterospondylic, and not mono- 

 spondylic, as in many other Selachians. The musculature and skeleton 

 of the mixipterygia, or copulatory organs, are dealt with fully for the 

 first time. 



What is a Monstrosity ? — 0. Abelj sums up the result of a long 

 discussion on this subject. It ended in adopting a definition given by 

 R. von Wettstein : — " A monstrosity is an occasional, non-pathological 

 deviation from the normal structure of an organ, which essentially 

 transcends the experimentally probable variability of the organ or the 

 organism." 



* Proc. Zool. Soc, 1910, pp. 540-71 (5 pis.). 



t Verh.Zool. Bot. Ges. Wien.lx. (1910) pp. 129-40. 



