54 



to the function of the ooecia. He has seen the formation of the egg in the 

 zooecium and while the ooecium originally was empty he found it at a certain 

 time containing an egg, without being able to ascertain how it came there. He 

 expresses the following supposition: »wahrscheinlich zwangt sich das Ei durch 

 den hohlen Stiel der Ovicelle und tritt durch eine Oeffnung, welche ich an der 

 Stelle, wo die beiden Blasen zusammenhangen, gelegen vermuthe, in den Raum 

 zwischen den beiden Blasen.« Nitsche tries to explain Hincks' different view, 

 that the eggs are formed by a granular mass in the ooecium in the following way, 

 that the egg after its transference to the ooecium instead of developing further, 

 sometimes dies away and dissolves into a shapeless mass. Finally, he states that 

 the supposed eggs, which Hincks has observed in zooecia without polypide, are 

 only peculiar bodies which have arisen from a retrogressive metamorphosis of 

 the polypide. 



In » Contributions to the history of the Polyzoas where Hincks' introduces 

 the new name »ooecium«, he admits the correctness of Nitsche's assertion, that 

 the supposed eggs, which he had discussed earlier, are really the so-called » brown 

 bodies*, and he assents to Huxley's view of the ooecia as marsupial chambers. 

 He adheres however to the idea, that eggs can now and then be formed in the 

 ooecia and maintains the correctness of the observations which he formerly made 

 on this subject in a few Bugula species and Bicellaria ciliata. In his later published, 

 principal work^ he definitely expresses the view that the ooecium has an internal 

 connection with the zooecial cavity (»its interior is in direct communication with 

 the perigastric cavity*), but otherwise there is no further information on the 

 structure of the ooecia. They are indicated as »prominent«, »subimmersed« and 

 » immersed* (Flustra, Cellarid), according as they are more or less prominent on 

 the surface of the colony or hidden within this. 



Vigelius' in his investigations on Fliis&a membranaceo-trimcata has given a 

 description of the structure and development of the ooecia in this species. While 

 the ooecium and its operculum in Bicellaria ciliata arise as two outpushings from 

 the frontal wall of the zooecium, the ooecium in this species arises as an inva- 

 gination from this wall, a short way distally to the operculum and it thus comes 

 to protrude into the zooecium as a hollow bladder, the interior part of which 

 enters into connection with the distal wall of the zooecium, which is here formed 

 in a peculiar way. It consists namely of a horizontal, under part, which origi- 

 nally reaches right to the frontal wall of the zooecium and of a distally and 

 slightly basally inclined part, which grows together with the ooecial bladder. 



• 38; « 22; ' 105, p. 



