330 



DISCOVERY REPORTS 



(1883) followed on a genus called by him Thysanopiis, but which according to the 

 description of the thoracic appendages was evidently the genus Thysanopoda. 



A general account of the reproductive system of the genus Euphaiisia was given by 

 G. O. Sars (1885) in his report of the Schizopoda of the Challenger Expedition, but no 

 adult male or female specimens were obtained and the account is therefore incomplete. 



Chun (1896) reviewed the previous work on the group and described the system in 

 Stylocheiron, giving an account of the histology of the ovary and testis. 



Zimmer (1913) worked on a considerable quantity of Eiiphausia superba Dana, and 

 although the material was not sufficiently well preserved for histological examination, 

 he was able to describe the general anatomy and to discuss the function of the various 

 structures. His account was supplemented by Raab's work, which appeared in 1915, 

 on Meganyctiphanes norvegica M. Sars and Euphaiisia krohnii Brandt. The material 

 available was specially preserved and Raab was able to employ histological methods; 

 consequently his descriptions are the most detailed of any published hitherto. 



None of the above workers, however, had access to such a large collection as that 

 made during the course of the Discovery Investigations, and they were therefore unable 

 to record a complete series of growth stages from the earliest appearance of the repro- 

 ductive system to sexual maturity. 



MALE REPRODUCTIVE SYSTEM 



The general plan of the male reproductive system can be seen in post-larval specimens 

 of 18-20 mm. in length, in which, however, there is as a rule no sign of modification 

 in the pleopods. 



ca^ ala ha t da vd g pn vd 



*Fig. I. Dissection to show the development of the male reproductive system. :■: 15. ala, anterior 

 lateral artery; ca, cephalic aorta; da, descending aorta; ^, gut; ha, hepatic artery; pa, posterior aorta; 

 /, testis; vd, vas deferens. 



The testis / (Fig. i) lies partly below the heart and partly on the dorsal surface of the 

 liver to which it is attached by a fold of mesentery. It consists of fifteen finger-like 



* Figs. 1-7 show progressive stages in the development of the male reproductive system. 



