10 W. T. CALMAN. 



Sexual Organs. — The sexual organs lie on the dorsal side 

 of the intestinal loop, the ovary being external or dorsal to the 

 testis. In all the individuals examined several ova were found 

 in various stages of development, the largest being about 

 •G mm. in diameter. They are contained in follicles opening 

 by short canals into the oviduct (PI. 3, fig. 27). No very 

 young ova were seen, the smallest being about "1 mm. in 

 diameter, and nowhere did the ovary present in section the 

 bilateral T-shape described by Maurice in Fragaroides and 

 by van Beneden and Julin in Clavellina. Inside the wall of 

 the follicle in all save the youngest there is a loose layer of 

 cells outside the egg-membrane (PI. 3, fig. 28). This seems 

 to correspond to the inner of the two layers into which the 

 follicular wall splits in Clavellina according to van Beneden 

 and Julin (' Arch, de Biol./ vi, p. 358), though in the latter 

 case the splitting does not take place until the ovum is nearly 

 ripe. Inside the egg-membrane are the characteristic and 

 problematical " test-cells,^^ with large nuclei each containing 

 several nucleoli, and scanty protoplasm. The vitellus becomes 

 more and more coarsely granular as the egg matures, and in 

 the oldest eggs it is broken up into numerous irregular yolk- 

 masses. The oviduct is a thin-walled tube running up alongside 

 the vas deferens (PI. 2, figs. 15 and 16). 



On the dorsal surface of the animal's thorax, near its junc- 

 tion with the neck and rather to the left of the mid-dorsal 

 line, there is attached by a narrow neck a spherical thin-walled 

 vesicle of about '5 mm. in diameter (PI. 1, fig. 3). The wall 

 of this vesicle is composed of two layers, the outer continuous 

 with the ectoderm of the thorax, while the inner seems to be 

 continuous with the wall of the oviduct. It is difficult to make 

 out the exact relations of the parts, but I believe that the lumen 

 of the oviduct opens into the vesicle. This organ occupies the 

 position of the incubatory pouch possessed by so many Com- 

 pound Ascidians, and its apparent connection with the oviduct 

 naturally suggests that it represents that structure, though I 

 have never found eggs or larvae in it in a single instance. 



In nearly all the specimens examined hardly a trace of 



