794 PROFESSOR W. C. M'INTOSH AND MR E. E. PRINCE ON 



form, in fact, the germinal epithelium, but a definite germinal ridge cannot be made out. 

 Indeed, in the haddock, it is not until the second or third week after extrusion that this 

 germinal portion becomes distinctively marked (PL XL fig. 14). Some of these cells 

 (po) are seen to enlarge and protrude from the surface of the mesentery (msn) into the 

 abdominal cavity as large primitive ova, and they occur, almost solely, slightly anterior 

 to the urinary vesicle, especially above the region of the small intestine. In short, their 

 appearance and distribution precisely accords with Balfour's description of the early 

 Elasmobranch ovum (No. 15, vol. xi. p. 161). The ova are most closely grouped on 

 the roof of the abdominal cavity, and especially in the median niches formed by the 

 projection of the suspensory septum or mesentery (msn). They are also grouped upon 

 the mesentery, and some develop upon or have migrated to the peritoneal envelope of the 

 intestine itself (hg). They are very irregularly distributed, and show great variation in 

 size ; large spherical ova projecting from a mass of small undeveloped cells, and all 

 loosely held together by the delicate connective tissue of the peritoneum. The ova 

 appear to be like the cells adjacent, and differ only in their larger size and more active 

 development. Each consists of a mass of minute nucleated spheres enclosed in a thin 

 membrane ; but are quite unlike the primitive ova of Elasmobranchs, as described by 

 Balfour (No. 13, p. 164), for these latter are uninucleate, one or two nucleoli, stain- 

 ing deeply, occurring in the nucleus, which is large, and surrounded by a granular 

 protoplasmic matrix. Along each side of this region of the abdomen, external to the 

 abdominal cavity, a mass of cells may occur, not unlike, but less in dimensions than, the 

 primitive ova described above. The lateral niche in which they are aggregated is defined 

 by richly pigmented peritoneum, and this pair of lateral sacs strongly suggests the 

 ovaries of the adult. The largest ova are those, however, which are free, and project 

 boldly from the mesentery and roof of the abdomen. Balfour speaks of a thickened 

 germinal epithelium in the Teleosteans, into which the adjacent stroma sends ingrowths — 

 the cells of the epithelial layer increasing by the growth of the clear protoplasmic 

 contents. But this does not correspond with the condition seen in the young haddock, 

 each ovum being a more or less perfect sphere, and enclosing numerous minute 

 nucleated bodies. Later stages were not observed, and it was not made out whether the 

 lateral peritoneal sacs finally became the ovaries with their continuous genital ducts, or 

 whether an epithelial layer grew over the freely suspended primitive ova, and enclosed 

 them in an ovarian sac, depending from the abdominal roof. 



