458 Miscellaneous. 



Chalina gractlenta spreads over stones and shells, and its gem- 

 mules, always in considerable number, become organized directly 

 against its support ; they are rounded, whitish, and generally 

 measure hardly more than 0-25 millim. in diameter ; they are found 

 disseminated or pressed against each other, and in the latter case 

 the envelope of each of them remains independent of that of its 

 neighbours ; here again the capsule is armed with spicules, but no 

 skeletal production traverses the cavity of the corpuscle, its small 

 dimensions rendering quite unnecessary the formation of an internal 

 framework. 



It is also in contact with the support, that is to say adherent to 

 the walls of the perforated galleries, that the gemmules of Cliona 

 vastijica are developed. They vary much in form and dimensions, 

 but they are distinguished at the first glance by the bright red 

 colour of their cells. They have only an incomplete envelope to 

 separate them from the mass of the sponge ; the calcareous substance, 

 riddled with little pits, upon which they are moulded, protects them 

 on the other side. The capsule contains no spicules in its substance, 

 but in general it is lined with a layer of these organites .arranged 

 tangentially to the mass and parallel to each other ; generally also 

 a few spicules are found scattered in the interior cellular mass. 

 The three kinds of spicules of the sponge may be combined in these 

 various positions, or one of them may occur to the exclusion of the 

 others. More rarely the gemmules are absolutely devoid of spicules. 



Lastly, what Carter called " the ovigorous layer of Suhentes do- 

 muncula " is by the last evidence a layer of true gemmules. We 

 know the part contributed by the English author to the knowledge of 

 the gemmules of the Spongilke, and yet in his note (Ann. & Mag. Nat. 

 Hist. 1883, xii. p. 30) he has not made the least allusion to these 

 asexual germs. 



The gemmules of Suberites doniuncula (of the Mediterranean) and 

 those of its near relative, S. Jicus (of the Channel), have the same 

 structure and occupy the same position. They are reduced to the 

 essential elements, a capsule and cells. Always in juxtaposition, 

 they cover with a continuous layer the shell or stone to which the 

 sponge is attached. 



Carter very well describes these reproductive bodies ; but having 

 observed that their capsule became thinner in contact with the sup- 

 port, he regarded them as ova incapable of development until such 

 time as, this support being destroyed, it becomes possible for the 

 embryo to make a passage through the thin portion of the envelope. 

 It is true that from what he says he had observed our Suberites Jicus 

 only on 6th January, 1870, and 4th September, 1877, at periods 

 when the gemmules in repose appeared to him like ova all in the 

 same stage of development ; now these germs are formed at the end 

 of summer and emit their contents in the spring by rupture of their 

 capsule : and if Carter had had the opportunity of examining Sub- 

 erites in May and June, he would have seen the capsules in position, 

 but empty, and ruptured on their convex side. 



At present Cliona vastijica is the only known sponge of which 

 the gemmules do not all arrive at maturity in the spring ; they may 

 be found all the year round in its lobes, even at the time when sexual 

 reproduction takes place. — Comptes Bendus, April 30, 1888, p. 1298. 



