and Functions of' the Sponge. \2& 



they present circular arrangements, and distinct openings are at 

 length perceptible, by the aid of a microscope at these inclosed 

 places. The ova spread and enlarge in every direction, they be- 

 come more compact in texture, more opaque and convex ; and, 

 before they exceed a line in diameter, they present through the 

 microscope a marked resemblance to the parent sponge. 



The ova make their appearance at very different seasons, in 

 different species of sponge, and the same species very probably, 

 varies its time of generating, according to its latitude. Olivi, 

 Vio, and Schweigger, observed these yellow ovate bodies only in 

 autumn in the sponges which they examined in the Mediterra- 

 nean, (Schweigger's Beob. auf R. R. p. 90). From the season 

 of their appearance, Olivi considered these bodies as grains, 

 while Vio and Schweigger considered them as ova, from their 

 believing the sponge to be an animal. The latter authors ob- 

 served, that they were distributed, without any apparent order, 

 through the gelatinous matter, and that they were of a somewhat 

 different colour from that matter, and more consistent. Schweig- 

 ger considered them as beings formed out of that matter, and capa- 

 ble of independent existence, — an opinion which happily accords 

 with the experiments above detailed. In the S. papillaris, S. 

 cristata, and S. tomentosa, on Leith rocks, the ova do not make 

 their appearance till spring. They are present in April, May, 

 and June ; and they exhibit the same mode of distribution 

 through the deeper parts of the animal, (fig. %\.f,f.), the same 

 ovate form, granular or vesicular texture, ciliated anterior sur- 

 face, mode of expulsion, and spontaneous motions, as in the *S'. 

 panicea. They have a darker yellow colour, and a more length- 

 ened posterior extremity, than those of the S, panicea, and we 

 can scarcely detect the rudiments of spicula in them, at the time 

 of their expulsion. It is somewhat remarkable, that, in the por- 

 tions of these species, which we frequently find of a deep sea- 

 green colour, the ova have exactly the same yellow colour, 

 as in specimens which present their more common yellow 

 hue. I have repeatedly performed, during two successive sum- 

 mers, the same experiments on these ova as those above 

 detailed, and with the same results. From the manner in 

 which these ovate bodies are formed in the parenchymatous 

 substance of the sponge, and their changes after expulsion. 



