156 Mr. T. Brightwell on a dioecious Rotifer 



June 17 th, a.m. — Placed four females with opake ova in a 

 trough by themselves. 



June l§th, 7 a.m. — Found two of the opake ova deposited and 

 all the four females dead. These ova were preserved eight or ten 

 days and underwent no change. 



June 24th, 8 a.m. — Isolated a female which had one clear ovum 

 and one opake as above. 4 p.m. — It had deposited the opake 

 ovum, which was occasionally examined for eight or nine days, 

 but no change was perceived. 



July 26th, 9 a.m. — Isolated a female having a small imperfect 

 dark ovum, about half the full size, adhering to the ovarium, and 

 also in the lower part of the body a full-sized semitransparent 

 ovum. 7 p.m. — Found the semitransparent ovum become opake, 

 and the small imperfect ovum a full-sized semitransparent ovum. 



July 27th, 9 a.m. — Found the opake ovum deposited. 



The ovarium when fertilized becomes tumid, somewhat dark, 

 and abounding in minute globules. From the centre, where it 

 appears divided, the ova are extruded. At first the vesicle is 

 very small and filled with the same fluid as the ovarium ; as it 

 enlarges the vesicle appears brownish and opake, enlarging by 

 degrees into the above-mentioned beautiful semitransparent, fol- 

 licled ova (see PL VI. fig. 6). 



Observations as to the Union between the Sexes. 



June 15th. — Placed a male and six females in a small glass 

 trough by themselves, and two males and about thirty females in 

 a large trough. 



June 16th, between 7 and 8 a.m. — On examining the small 

 trough observed that the male on approaching one of the females 

 attached himself to its side by the spermatozoid projection, and 

 remained so attached from twenty to thirty seconds. The same 

 male acted precisely in the same manner with four other females. 

 These five connexions took place in about fifteen minutes. 



At 8 a.m. — Watched the two males in the larger trough more 

 than half an hour, the males swimming close to many of the 

 females, but no conjunction took place. Observed the males 

 frequently attach themselves to the glass by their heads and 

 distend their bodies. 



At 5 p.m. — Saw one of the males in the larger trough attach 

 himself to a young one of the other sex for about twenty seconds, 

 and afterwards to a full-grown female for a somewhat longer 

 time. Saw this last connexion in a clear light most distinctly. 

 The end of the sperm-tube was attached to the side of the female, 

 and the rest of the body of the male was quite free. Saw the 

 same male soon after fix itself by its head to the glass and re- 

 main so for thirty seconds, and during this time it continued 



