343 Mr. H. J. Carter on the Seed-like Body of Spongilla. 



(p. 67), since I presume that both allude to the Xanthidia; for 

 Prof. Allman states himself that the Polyzoa are frequently- 

 associated with Spongilla, and in Bombay they may be consi- 

 dered the only associates of this organism : they not only abound 

 in the same tanks, but they live and thrive imbedded in the 

 surface of Spongilla, which is destruction to any other organism ; 

 nay, more^ the statoblasts, under certain circumstances, may be 

 found imbedded in the midst of the statoblasts at the base of 

 the Spongilla, whither they have probably been carried by the 

 inward currents, after having fallen into the oscula as they were 

 discharged from the Lophopus. Now, when we know that these 

 animals are the associates of the Sponges, that the latter are 

 petrified into flints in the chalk, &c., in which flints these Xan- 

 thidia are found, and that the Desmidiese are not to be found 

 except by accident where the Sponges are, not being of the same 

 habitat, it does seem to me, while all three bodies, viz. the orhi- 

 cular statoblasts with marginal spines, sporangia of Desmidiese, 

 and Xanthidia, are extremely alike, that the probabilities, if not 

 the actual forms, are more in favour of the Xanthidia being the 

 petrified orbicular statoblasts of the Polyzoa than the petrified 

 sporangia of Desmidiese. 



P.S. On placing some vertical sections of the statoblast of 

 the Lophopus in Canada balsam for examination, I find that the 

 " equatorial plane " round the coriaceous coat was a deception : 

 there is a plane ; but it is formed by the contact of the upper 

 with the lower layer of cells of the cellular coat, and not by an 

 extension of the coriaceous coat, as seen in fig. 10, where the 

 thick dark line, c, should be represented by a very thin light 

 one, and the cells restmg perpendicularly on it. 



Bombay, Feb. 1859. 



EXPLANATION OF PLATE VIII. 



N.B. In order to convey an idea of the Velative proportion of the figures, 

 as they are intended for comparison, several have been drawn on the 

 same scale. Thus, figs. 1, 3, 8 & 10 are on the scale of l-48th to 

 l-1880th of an inch ; figs. 2, 4, 9 & 11 on that of l-6th to l-1880th of 

 an inch, that is, eight times greater than the foregoing; and figs. 5, 6, 

 7, and 12, 13, 14 on the scale of l-12th to l-5400th of an inch. 



Fig. 1. Spongilla Carteri, Bowerbank, statoblast of, about l-31st of an 

 inch in diameter : a, coating of small spicula ; 6, surface of cel- 

 lular coat (here the ends of the hexagonal columns have been 

 drawn circular, to save time and trouble) ; c, hilum or infundi- 

 buliform hole leading into the cavity of the coriaceous coat (see 

 fig.3c^). 



Fig. 2. Ditto, ditto, portion of the surface of the cellular coat, more mag- 

 nified, showing the hexagonal form of the cells,-— a Uttle more 

 regular th^n it is in nature* 



