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Part III. — Sixteenth Annual Report 



flat, semi-translucent gelatinous band, soft and easily ruptured, and 

 suspended by a broad but delicate mesovarium (Plate II., fig. 1, a). The 

 ovaries form a continuous tube, the oviduct (6), which is thick-walled and 

 narrow — admitting a linger with difficulty — opens into it at its middle, 

 at the junction of the ovigerous and non-ovigerous sides. The ovigerous 

 tissue is limited to one side of the tube, the opposite wall of the ovary, 

 which at this stage is a very thin, delicate, translucent membrane, being 

 closely applied to it. On section, therefore, across the length of the 

 ovary the appearance is as shown in fig. 4, the ripe or nearly ripe eggs 

 being arranged in a single layer, imbedded in the tenacious gelatinous 

 matrix. 



At an earher stage the non-ovigerous wall is considerably thicker 

 (Plate II., figs. 8, 9). No free fluid is present in the ovaries. When a 

 portion of the ovigerous wall is cut out and placed in sea-water it swells 

 up considerably from the absorption of water, the gelatinous matrix 

 becoming mucoid, glairy, and slippery; if it is left exposed to the air it 

 dries up to form a thin film or layer from which the eggs project. The 

 gelatinous matter does not lose its transparency or become white in 

 w^ater or by boiling, and as the eggs become chalky-white under these 

 conditions the piece of ovary looks a mass of half-boiled sago. The 

 ovigerous layer scraped off from the ovary floated in sea water of 1026 

 specific gravity (temperature 16'8°C.), and the eggs, unless carefully 

 separated from the mass, also float owing to adherent mucoid matter. It 

 is a little difficult to detach the eggs without rupturing them, owing to 

 their very thin capsules ; but when this is done they sink in sea-water, 

 although not so rapidly as thick-shelled demersal eggs like those of the 

 lumpsucker. Dr. Milroy determined the specific gravity of the detached 

 eggs to be 1*034. 



On dissecting a piece of the ovigerous wall, which has been hardened 

 by spirit or by boiling, especially before the eggs are quite mature, it will 

 be found that each large egg is contained in a pyriform pouch which pro- 

 jects into the cavity of the ovary, and which, in such specimens, may be 

 easily separated at its pedicle (Plate II., fig. 7). It may also be observed 

 that within this pouch at its base there are several small eggs. Hence the 

 internal surface of the ovigerous layer in such specimens has a papillose 

 appearance. 



The structure and formation of the ovigerous pouches are better under- 

 stood from mounted sections. From Figures 8 and 9, Plate II., it will be 

 seen that at the point where the smooth barren Avail of the ovary passes into 

 the ovigerous wall the latter is split into two more or less distinct layers, 

 separated by a thin, loose, mucoid or cellular tissue in which are numerous 

 blood-vessels. The connective tissue fibres in the thin outermost layer 

 are for the most part transverse ; those in the thicker inner layer are 

 principally longitudinal. The loose intermediate tissue is full of lacunae, 

 or lymph spaces, which become more marked as the ovary ripens, and are 

 continuous with the interior of the ovigerous pouches. The pouches are 

 formed by digital ingrowths of the epithelium lining the ovarian cavity 

 and of the subjacent connective tissue stroma, which carries blood capil- 

 laries with it. Each of them at an early stage contains a number of eggs, 

 it may be about a dozen, two, three, or four of the most distal being at 

 this time sub-equal in size ; but as growth proceeds one of the eggs 

 develops much more rapidly than the others and comes to occupy the 

 whole of the cavity except the stalk. The other eggs remain in a 

 stationary condition without forming yolk. In the mature ovary they 

 are crowded and distorted at the base of the large egg in the pedicle of 



