26 Mr. II. J. Carter on the Anatomy 



On the 12th of May last year (1874). The same. Ova 

 about 7-6000ths of an inch in diameter, passing and having 

 passed in many instances into the embryonic state (Gastrula, 

 Hackel). No appearance of spermatozoa. Living and active 

 specimens of this gathering were also examined on the 13th, 

 14th, and 15th respectively, with the same results. 



On the 16th of May, 1874. The same, but with more 

 embryos. No appearance of spermatozoa. Living and active 

 specimens of this gathering were also examined on the 17th, 

 with the same results. 



On the 18th of May 1874. The same in every respect. 

 Living and active specimens of the same gathering were ex- 

 amined on the 20th, when the spermatic-looking bodies, loose 

 and apparently dead (figured in plate x. fig. 21 I.e.), were 

 observed. 



On the 25th of May 1874. The same in every respect, with 

 the exception of more embryos and fewer ova, but no sperma- 

 tozoa. 



So far, therefore, as my own observations are concerned, I 

 cannot say with certainty that I have yet seen the spermatozoa 

 of any sponge. 



The little calcareous sponge Grantia compressa has been 

 chosen for examination, from the following circumstances, 

 viz. : — that it is very hardy, grows on branches of Ptilota 

 midway between high and low-water marks, may therefore 

 be obtained twice a day and thus gathered without injury ; 

 while its breeding-season is now determined ; hence, perhaps, 

 where it abounds, it furnishes the best sponge for discovering 

 the spermatozoa. 



Epitomism of the Ampullaceons Sac. 



Thus, then, the " ampullaceous sac " is an epitome of the 

 whole sponge, in so far as it has an inhalant and an exhalant 

 aperture, and contains the spongozoon or animal of the sponge 

 in plurality, which again has its oral and anal apertures respec- 

 tively, together probably with all the other organs in its body, 

 capable of nourishment and reproduction. 



Pore- System and Dermal Cavities. 



The pore-system may be divided into the " pores " on the 

 surface, and the " subdermal cavities " with which they are 

 immediately connected ; while each division, being equally 

 important, will be separately described. 



