852 



Mr. H. J. Carter on the Reproductive 



side and on the other, or outside, in continuation with the beaks 

 of the spongozoa (woodcut, d) ; while the germinal vesicle 

 which is spherical, averages 2-6000ths in. in diameter, and 

 the germinal spot, which is circular and opaque, about 

 l-6000th in. ; so that the interval between the ovum and outer 

 border of the ampullaceous sac is filled up by the spongozoa (a). 

 Now, when the ovigerous portion of the sponge is torn to 

 pieces for microscopic examination many of the ova become 

 detached or separated, and tlien they are seen to be fringed 

 circumferentially with the filamentous remains of the beaks 

 of the spongozoa, which, radiating from them all round, kept 

 the ovum in position within the ampullaceous sac {d). 



ff, oTTim as seen under deep focussing, in wliicli tlie spongozoa 

 surrounding it are only visible ; h, ovum under less deep focussing, in 

 wbicli the whole of the spongozoa covering the ovum come into vieAv ; 



c, oviun in the cell of the ampullaceous sac without any spongozoa ; 



d, ovum out of the ampullaceous sac, showing the capsule with shreds 

 of bealis of spongozoa attached to it. 



There is no difficulty whatever in seeing all this clearly in 

 a well-preserved specimen when the sections are thin and 

 mounted in glycerine, especially when stained. 



Every ampullaceous sac on the inner portion of the sponge 

 (where the ova are, as usual, chiefly developed) contains a 

 single ovum about the size mentioned, and on no occasion 

 have I observed more than one, nor have I been able to dis- 

 tinguish anything like a spermatoid development. I state 

 this because hereafter I shall have to notice another specimen 

 of the same species in which there appears to be a spermatoid 

 development without any ova. 



It must therefore be inferred that in this instance the ovum 

 is developed loitliin the ampullaceous sac, that it originated 

 there, and that finally it would, in the embryonal state, find 

 its way through the opening of the ampullaceous sac (which 

 by that time, from the enlargement of the ovum, will probably 

 have become totally effaced) into the excretory canal. Thus 



