18 Mr. H. J. Carter 07i the Suhspherons Sponges. 



the growing again inwards of the spicules, so as to fill up the 

 cavity to their original " central point " of departure. 



It is needless to criticise this deliberately detailed statement, 

 which is by no means borne out by the figures intended to 

 illustrate it, whatever the bodies may have been from which 

 these were taken (Brit. Spong. pi. 22. fig. 327, and Phil. 

 Trans.). It must have been as difficult, one would think, 

 to obtain all this information with the microscope as for a 

 closed siliceous cavity to form itself in the central point of a 

 radiating mass of spicules, then secrete ova in its interior, 

 then form a hole for their exit, and then close its cavity up 

 again so as to become a compact ball of silex, termed by the 

 author an " adult " or " mature ovarium " (!) (Phil. Trans. I.e. 

 p. 815 ; Brit. Spong. vol. i. p. 143). 



Alluding to these globular crystalloids in Pachymatisma^ 

 Dr. Johnston, with his natural modesty and love of truthful- 

 ness, observes : — " The bodies which Dr. Bowerbank has de- 

 scribed as the gemmules of its crust are, he writes me, very 

 much alike in structure to the granules of the Geodia, which 

 he finds also occur in the body of this sponge as well as in the 

 crust. This suggests the query whether the cuticular gra- 

 nules of Geodia may not be truly gemmules ; but I confess 

 that to me it appears the question should be answered in the 

 negative. Their position, their siliceous and crystalline cha- 

 racter, and the mode of their aggregation, seem all opposed 

 to it, and not less so the difference between them and the 

 recognized gemmules of some Halichondrise." (Hist. Brit. 

 Sponges, p. 202.) 



It seems to me that if the globular crystalloids of the crust 

 of Geodia are to be considered ovaria, the large stellate bodies 

 of Tetliya lyncurium, which are similarly situated and very 

 nearly as large (bearing the proportion of 6 to 8), should also 

 have this distinction ; but these are called by Dr. Bowerbank 

 " stellate spicula." (Brit. Spong. vol. ii. p. 92.) 



Again, in a compound tunicated animal, about the size and 

 shape of half a small pea, which, although probably described 

 before, I have but just noticed on the branches of the fucoid 

 Cystoseira grannlata, in juxtaposition with Grantia ciliata^ 

 the mass, which is of the whiteness of snow, is chiefly com- 

 posed of globular crystalloids of carbonate of lime, presenting 

 conical points all over them, very similar to fig. 13 «, PI. I. 

 This crystalloid, wlicn compared with that of Geodia arabica, 

 bears tlie proportion in diameter of 3 to 8, but, although much 

 smaller and composed of carbonate of lime instead of silex, 

 has exactly the radiated mineralogical structure of tlie globular 

 crystalloids of Pacliymatisma and Geodia arabica (fig. 12, a. 

 PI. I., and fig. 14, r,V>, PI. II.). 



