398 Prof. J. Reid on the Anatomy and 



cured about the middle of October, these ovary-capsules were 

 more or less filled with opake bodies (ovaries) of a slightly yel- 

 lowish colour. Each of these bodies was composed of small 

 nucleated cells inclosed in a membrane. The external surface of 

 this membrane was in many of them provided with cilia in mo- 

 tion, causing some of them to perform a rapid rotatory motion 

 within the ovary-capsules. These ova in the first stage of their 

 growth adhere to the upper end of the lining membrane of the 

 capsule. This lining membrane stretches across the aperture in 

 the capsule, and also sends a reflection across the cell imme- 

 diately below the ovum so as to inclose it in a kind of sac, leaving 

 however, in the young ovum, a space between them. In the more 

 advanced ova, this membranous partition was much thickened, 

 especially at the central part, forming a considerable projection 

 in the direction of the aperture in the capsule, and contained a 

 number of nucleated cells. When the ovum enlarges so as to 

 fill the interior of the capsule, it pushes this membranous parti- 

 tion before it. This membrane was observed in a few instances 

 where the ova were fully formed to contract and relax at in- 

 tervals, and in this way it may assist in the escape of the ovum. 

 On detaching some of the ovary-capsules with the view of ex- 

 amining their contents under a high power, one of the ova was 

 seen partially extruded from the aperture in the capsule. It 

 was divided by a deep fissure into two unequal parts, the 

 largest of which was nearly entirely outside the capsule (fig. 

 13 «). The extremity of the largest portion (fig. 13 c) was di- 

 stinctly prolonged, more translucent than the rest of the ovum, 

 and presented along its free edge a row of hairs resembling 

 cilia, which, however, remained quite motionless, while along the 

 whole of the rest of the external surface of both portions, except 

 upon the edges of the fissure, cilia were in such vigorous action 

 that it was impossible to distinguish them individually, and they 

 produced the appearance of the rim of a wheel in very rapid 

 rotation. After the lapse of an hour the fissure had extended 

 through the whole body of the ovum, and the larger portion (fig. 

 13 6) being set free, swam about very actively in the water; but 

 all this time the hairs attached to the prolonged anterior portion 

 remained motionless. The smaller portion continued in the cap- 

 sule, and performed very rapid rotatory movements. This was 

 the only ovum I observed in the act of escaping from the inte- 

 rior of the capsule, but I had an opportunity of watching three 

 other bodies exactly similar to the larger portion of the ovum 

 already described, when examining other portions of the same 

 polypidom. One of these had become fixed, by the hairs attached 

 to the anterior extremity, to a minute portion of sea-weed, arid 

 the cilia were in active motion. When examined ten hours after. 



