260 GILBKRT C. BOURNE. 



are full of ova in all stages of maturation. The I'lper ova are 

 relatively large^ are full of large yolk-granules, and are enclosed 

 in follicles and furnished with reserve cells after the manner 

 common in Ascidians. The dorsal ends of the two ovaries 

 are continued into short oviducts, which ran in the ecto- 

 plerome and open into the atrial cavity at the ends of two 

 papilliform prominences situated a short distance in front of 

 the anus opposite the entrance of the atrial siphon {E.od., 

 L. od., figs. 34, 14, 21). The terminal sections of the oviducts 

 are lined by a ciliated cubical epithelium. 



The testes are a mass of ramified tubules closely applied to 

 ventral and ventro-lateral surfaces of the distal limb of the 

 stomach. There is no external indication of their being 

 paired, nor can any sign of paired structure be discovered in 

 sections of these organs; but the sperm-ducts are paired and 

 open at the ends of rather conspicuous nipple-shaped promi- 

 nences into the right and left peribranchial cavities close to 

 the angle of flexure of the stomach. Fig. 22 is a representa- 

 tion of the left spermiducal opening with an adjacent lobe of 

 the testis, and incidentally illustrates the structure of the 

 gastric and intestinal epithelium and of the connective tissue 

 of the ectoplerome. In the testicular tubules one can distin- 

 guish externally a peripheral mass of larger rounded or 

 polygonal colls with conspicuous nnd deeply stained nuclei ; 

 these I take to be spermatogonia ; within these a layer of 

 smaller cells, which seem to be spermatocytes, and in the 

 centre a mass of developing spermatids, and in some of the 

 tubules bundles of filiform spermatozoa. The celhilar elements 

 are minute, and the organ was too much macerated to admit 

 of detailed study. 



The Blood-vascular System. 



I found traces of the heart in the form of a thin-walled, 

 muscular tube, lying in the angle between the posterior end 

 of the renal organ and the lobes of the testis ; its position 

 is indicated at Uf. in lig. o4. The muscular tube is 



