HUXLEY, ON THE CHEILOSTOME POLYZOA. 191 



great difficulties to those who possess leisure and the oppor- 

 tunities of a sea-side residence ; and to any such person, 

 whose eye may fall upon these pages, I commend the investi- 

 gation as one which will amply reward him. 



Note on the Reproductive Organs of the Cheilostome 

 PoLYzoA. By T. H. Huxley, F.R.S. 



Obvious as are the ovicells and partially-developed ova of 

 the cheilostome Polyzoa, the precise position of their ovaria 

 and testis has not yet been determined ; the general idea that 

 the ova are developed within the ovicells being wholly an 

 assumption. The investigation of the question is not without 

 difficulty, on account of the delicacy of the ova in their young 

 condition, the greater or less opacity of the ectocyst, and the 

 obstruction offered by the other viscera if the cells be viewed 

 in any of the positions which they ordinarily assume, lying, 

 that is, on their front or back faces. By tearing up a 

 polyzoarium, with needles, into single series of cells, and 

 causing one of these series to lie upon its side, I found the 

 process of examination much facilitated. 



In the younger cells of Bugida avicularis, I find that, as in 

 many of the hippocrepian Polyzoa, there is a cord, or 

 funiculus, connecting the extremity of the stomach with the 

 bottom of the cell, and attached to this I found, close to the 

 stomach, a single small pale ovum, commonly possessing a 

 double germinal spot. At its lower attachment, on the other 

 hand, the funiculus is surrounded by a mass of minute, pale, 

 spherical corpuscles. In these cells, no ovicells were as yet 

 developed ; but in older cells they make their appearance as 

 diverticula of the ectocyst and endoc^st, having their internal 

 cavity continuous by a narrow neck with that of the cell. 

 A valvular aperture eventually becomes developed at the 

 lower part of their anterior face. 



In such older cells, the ovicell is at first empty, and we find 

 the ovum iittached to the funiculus increasing in size, and 

 acquiring a reddish coloration ; but in those still further 

 advanced, a similar, but larger and redder, body makes its 

 appearance in the ovicell, and after vmdergoing yelk-division 

 becomes a ciliated embryo. In these older cells, again, we 

 find the granular mass at the bottom of the cell gradually 

 developing into a mass of spermatozoa, which eventually 

 float loose in the cavity of the cell, 



I have no doubt, therefoi'e, that in Biu/ula avicularis the 

 ovarium is situated at the top of the funiculus, the testis at 



