88 Notes on the Ascidea Manhattensls^ De Kay^ 



calices filled with mature ova, with the vesicles of Purkinje 

 and the vesicle of Wagner (the latter appears first in the 

 calyx, the former already in the germinative follicle, and such 

 representing different stages of their development), — I watched 

 from day to day for the ejection of the ova, and was fortunate 

 enough to observe, on the 18th of July, 1851 (at high water), a 

 viscid, yellowish substance deposited on the mantles of innumer- 

 able specimens attached to the sideboards of the bathing-house 

 already mentioned, and on such only, which had been exposed 

 to the rays of the sun during the afternoon, the tubes of which 

 were directed more or less upwards,* which contained, as I 

 anticipated, the fecundated ova. On examination of the 

 ovaries of those specimens on which it was deposited, they were 

 found flattened and almost empty, and when I examined under 

 the microscope (300 diam.) the substance itself, I found that it 

 . contained mature and immature eggs and spermatozoids, both 

 identical with those contained at the time in the ovaries and 

 testes of full-grown specimens. Among the ova I noticed such, 

 in which the process of segmentation had commenced already. 



According to A. Krohn'sf investigations of the development 

 of the Ascidians, who observed the development of the ova of 

 the Phallusia mammillata (Cuv.), artificially fecundated, that 

 process begins within two or three hours after the spermatozoids 

 have come in contact with the ova. The ova which I observed 

 about 5 o'clock p.m. were ejected therefore probably at about 

 2 or 3 o'clock p.m. — under altered circumstances perhaps 

 earlier — on the same day. This observation proves conclu- 

 sively what Cuvier and von Baer, and more recently Krohn, 

 expressed as an opinion that, with some simple Ascidians, 

 {Phallusice), the ova are actually fecundated during their pas- 



* Wherever the animals are attached below stones or boards, etc. , the tubes 

 being directed downwards, the viscid fluid containing the fecundated ova 

 necessarily sinks to the ground, or is carried away by the current of the 

 water. 



f Ueber die Entwicklung der Ascidien ; Joh. Miiller's Archiv. Berlin, 1852, 

 p. 313. 



