Mr. H. J. Carter on the Suhspherous Sponges. 17 



questionable whether the whole of those formed in the crust 

 are not entirely developed there. 



Be this as it may, they begin their development, and for 

 some time follow it, very much like the radiated crystalliza- 

 tion of minerals, viz. first commencing from a central point, 

 surrounded by radiating hair-like spicules, which finally be- 

 come consolidated into a globular mass. Here, however, they 

 leave the spheroidal or mineral for the organic form, and be- 

 come oval, compressed, provided with an umbilical depression 

 in the centre, and a surface of clavate tubercles with more or 

 less flat or conical heads according to their position. 



It is remarkable also that, in the vertical section caused by 

 fracture, the body is found to have become a clear crystalline 

 solid globule, still faintly showing the radiated lines of its early 

 structure extending from the centre to the circumference (PI. I. 

 fig. 12 a, & PL II. fig. 14 h). On no occasion have I been able 

 to detect a central cavity in any stage of their development, 

 either in their natural state or after having been exposed to a 

 red heat, when the axial canals of the long spicules almost 

 invariably become expanded, and indicate, from their charred 

 appearance, the presence of more or less animal matter. At 

 whatever period, even under these circumstances, the crystal- 

 loid was broken, whether in its early unconsolidated hair-like 

 or in its subsequent crystalline compact state, the same struc- 

 ture was continuous from the centre to the circumference ; 

 there was no appearance of central cavity. Thus, however 

 much they resemble the seed-like bodies of Spongilla in ap- 

 pearance, they totally differ from them in their structm-e and 

 in their natiu-e. The seed-like body of Spongilla is incompa- 

 rably larger, commences as a simple spherical soft cell, look- 

 ing like a white speck imbedded in the sponge, and finally 

 becomes coated with its horny or siliceous spicular cortical 

 coat, as the case may be. (Annals, 1849, ser. 2. vol. iv. pi. 3. 

 fig 6 ; and 1859, ser. 3. vol. iii. pi. 8. fig. 3.) 



To these globular crystalloids Dr. Bowerbank has applied 

 the term " ovaria," stating that, " In an early stage they 

 appear as a globular body of fusiform acerate spicula, radiating 

 from a central point in the mass " (Phil. Trans. 1862 ; Brit. 

 Spong. vol. i. p. 141), that in the midst of this central point 

 " a central cavity is produced in which the incipient ova very 

 shortly appear," that the inner and acute terminations of the 

 radiating spicules form " the common inner surface of the 

 cavity of the ovarium, which is now filled with an opaque 

 mass of ova," that " a single conical orifice or foramen has 

 also been produced in a portion of the wall, through which the 

 ova are destined to be ejected," and that this takes place by 



Ann. d: Mag. N. Hist. Ser. 4. Fo^. iv. 2 



