THE REPRODUCTIVE SYSTEM OF E. SUPERBA 



331 



follicles arranged round the outer side of a horseshoe-shaped band. The anterior follicles 

 are short and broad, but the median and posterior ones become gradually more elongated. 

 The number of follicles appears to be fairly constant, there being generally seven on 

 each side and one occupying a median, anterior position. In the young specimen, each 

 follicle is distinctly separate from its neighbours, but in the adult all the follicles become 

 closely crowded together, although never actually fused. 



The vasa deferentia vd (Fig. i) run backwards from each end of the horseshoe-shaped 

 band. They are paired, slender ducts lying below the heart and extending back as far 



t vd 



Fig. 



2. Dissection to show the development of the male reproductive system. ■' 15. ega, external 

 genital aperture; g, gut; pfi, posterior flexure; t, testis; vd, vas deferens. 



as its posterior margin. At this point, each duct bends outwards at right angles, runs 

 between the musculature of the body wall and the carapace, and passes laterally and 

 ventrally behind the luminous organ, to open on the sternum of the eighth thoracic 

 segment near the middle line. The vasa deferentia are slightly dilated immediately 

 behind the external genital apertures ega (Fig. 2). 



As can be seen from the diagrams, the heart and some of the main blood vessels^ 

 are closely associated with the reproductive system. The hepatic artery ha runs into the 

 lobes of the liver immediately behind the median anterior testicular follicle (Fig. i), 

 while the cephalic aorta ca and the anterior lateral arteries ala branch off immediately 

 in front. The descending aorta da passes between the vasa deferentia to the ventral 

 body wall, and the posterior aorta pa leaves the heart just above the right angle bend. 

 The intestine is ventral to the reproductive system. 



As growth proceeds, the vas deferens becomes slightly swollen in the region of the 

 right angle bend, and a flexure pjl appears, so that there is a short anteriorly directed 

 part from which the duct runs outwards and backwards to the external opening (Fig. 2). 



1 The names of the blood vessels are taken from Zimmer's account of the Euphausiacea in Kiikenthal 

 and Krumbach's Handbuch der Zoologie, vol. iii, pt. i, 1926-7. 



