308 TOILERS IN THE SEA. 



species both methods may prevail. We cannot be 

 expected to discuss at length, and in detail, a point 

 of this character in a work like the present, but 

 would refer those interested in the subject to the 

 Introductory chapter of the volume already quoted. 1 

 The ovary varies considerably in size ; in some 

 species it contains as many as thirty eggs, in others 

 only one or two. At a certain stage of maturity they 

 make their escape, through the ruptured wall of the 

 ovary, into the space between the polype and the 

 inner wall of the cell. After fertilisation the ova pass 

 through the ordinary phenomena of segmentation, 

 and are developed into free ciliated larvae. In some 

 species there is developed, during the breeding season, 

 a small somewhat globose appendage to the mother- 

 cell, called an ovicell, the interior of which is in direct 

 communication with the internal cavity of the mother- 

 cell. At first the ovicell is empty, afterwards it is 

 occupied by the embryo. Huxley was the first to 

 observe that impregnation takes place in the cavity 

 of the cell, and then the egg passes from thence into 

 the ovicell, where, as in a marsupial pouch, it under- 

 goes its further development, and after undergoing 

 yelk-division becomes a ciliated embryo. 2 Mr. Hincks 



1 Hincks, "British Marine Polyzoa." London, 1880. 



2 J. H. Huxley on " Reproductive Organs of the Cheilostome 

 Polyzoa/' in Quart. Jour. Micr. Soc., vol. iv. (1856), p. 191. 



