96 



Part III. — Sixteenth Annual Report 



larger than the others ; and there is a tendency for the nucleoli to be 

 disposed peripherally. This condition was found in the haddock, 

 whiting, lemon sole, plaice, gurnard, common dab, and eel. In the 

 last the presence of usually one, but sometimes two or three very 

 large nucleoli, highly stained and refringent, is obvious (Fig. 6, PI. I.) ; 

 for example, in an ovum measuring O'OSmm., the germinal vesicle of 

 which had a diameter of 0 •043mm., the germinal spot measured 

 0 •020mm. In the lemon sole two or three similar large nucleoli were 

 sometimes present, but much smaller relatively than in the eel. In the 

 John Dory {Zeus faber) there are also present one or two large refringent 

 highly-stained nucleoli, containing a still brighter point or granule in the 

 interior. In sections of the ovary of a sole containing mature eggs, and 

 stained with hreinatoxylin, safFranin, and eosin, the small ova, measuring 

 about O'Smm., had in many cases two, and sometimes three, nucleoli 

 larger than the others. In this preparation the intra-nuclear network is 

 well seen, its appearance under a high power indicating a coarse network 

 with large meshes extending equally throughout the nucleus. 



In eggs a little larger, from about 0*09 to 0'18mm., a marked feature 

 is the very general disposition of the nucleoli around the periphery of 

 the germinal vesicle, which has at this time a distinct membrane, smooth 

 and regular in outline. It is also relatively large, and its sharp, distinct 

 contour suggests a swollen condition. In the sections of the ovary of 

 an immature haddock, caught in July, which was hardened in picro- 

 sulphuric acid, the ova range in size from 0*08 to 0 1 6mm., and possess 

 the following characters : — The germinal vesicle is relatively very large, 

 and may measure as much as 0"llmm. in an ovum of the largest size 

 stated. It is spherical, has a definite, quite smooth, regular contour, and 

 the contents, which have not shrunk from the membrane at any part, 

 are greyish and unstained, and under a high power show a finely granular 

 appearance. The nucleoli are subequal in size, and are disposed at fairly 

 regular intervals in close contact with the nuclear membrane, and 

 frequently flattened against it ; they number from six or seven to over 

 twenty in a section, and are relatively very small compared with the 

 germinal vesicle. The protoplasm around the latter is highly stained, 

 and shows the usual granular or reticulated appearance, and yolk 

 granules are absent. In the ovaries of an immature common dab, caught 

 on 2nd August, and presenting much the same general appearance, the 

 ova reached a size of 0 "IB 2mm. The germinal vesicle and nucleoli 

 resembled those of the haddock, but among the larger eggs the outline 

 of the former was less sharp and pronounced, and was somewhat wavy 

 or irregular, and at certain points towards the periphery yolk-granules 

 were present. In the ovaries of a gurnard, caught on 10th October, and 

 in which degenerating eggs were present, the ova at this stage showed 

 the granular zone sharply marked off. In the haddock previously 

 referred to, which was caught in August and had previously spawned, a 

 narrow granular zone at the periphery was evident in eggs 0-19mra. in 

 diameter, and the germinal vesicle and nucleoli had the same character 

 and disposition as in the immature haddock. In an immature whiting, 

 caught in July, the largest eggs measured 0*1 3mm. ; the germinal vesicle 

 was large and sharply defined, the nucleoli peripheral, and no yolk- 

 granules were present. In the ovaries of a plaice, caught on 20th 

 September, in which the large yolked eggs for the next spawning reached 

 about 0-58 mm., and made up the great mass of the organ, the smaller 

 eggs showed the same condition of the germinal vesicle, the nucleoli 

 being disposed around the margin in close apposition to the membrane. 



