RHINCALANUS GIGAS 



317 



posterior part of the saddle-shaped ovary. The oviducts appear as a fine cord of trans- 

 parent cells on either side of the body (Fig. 17 a). As maturity approaches the anterior 

 and ventral border of the saddle-shaped ovary takes on a deep brown colour in the pre- 

 served specimen and can be seen to be made up of a line of large dark cells each with a 

 circular nucleus (Fig. 17 b). This border of enlarged cells, the young eggs, extends from 

 the most anterior part of the ovary under the carapace along the ventro-lateral margin 

 of the gonad and oviducts to the genital opening. The ripening eggs become larger and 



3?,^-' 



I 

 z: 



I- 



i 



a b c d 



Fig. 17. Rhincalamis gigas. Adult females. Condition of the ovaries, a. Unripe, b. Maturing, c. Ripe. 



d. Spent. 



darker as maturity approaches, and, when about to be shed, they appear as very large 

 dark circular, discrete cells, resembling a string of beads, forming a conspicuous row along 

 each side of the thorax from the most anterior part of the ovary in the centre of the 

 carapace to the genital opening (Fig. 17 c). Towards the end of the season many females 

 appeared in the samples in which the only sign of a gonad was a thin transparent string 

 of tissue on either side of the posterior segments of the thorax (Fig. 17 d). No cell limits 

 were distinguishable in this, and it was assumed that these were "spent" females which 

 had shed their eggs. 



