of the Sponges to the Corah. 23 



development of Spoiigt'IJn, he would not have given a prefer- 

 ence to the Calcispongia' for tliis purjtose. 



It is reniarkaljje that Hiiekel, with the exception of stating at 

 p. Ill tliat " tl»e simple and extremely signiheant fact that the 

 reproductive cells are produced, by division of labour, from 

 the nutrient vibratile cells of the entoderm or vegetative genn- 

 lamcUa aj)plics to the sponges equally with the Aeale])hs," 

 never once alludes to the organs of nutrition^ by which the 

 sponge-structure is built uj) and sustained. Such an omission 

 could never have occurred with an obsen'ant, sagacious mind 

 like his, ardent in the j)ursuit of truth, had lie added to his 

 indefatigable researches on tlie calcareous sponges a study of 

 the develojjmeut of SpongiUaj such as I have described, or 

 even had he experimented after a like manner on the ficnig 

 calcareous sponges. 



Hiiekel observes, at p. 9, that the calcareous sponges to 

 which he has given the names of Ch'stosgca and Cophosyca^ 

 which do not possess an excretory opening, are probably to be 

 regarded as retromor|)hosed forms, related to tlie otliers as the 

 Cestode worms to the Trematoda. At p. 10, that " the part 

 played " by the cutaneous pores, which, in the corals, are the 

 peripheral extremities of the coelenteric vascular system, " is, 

 unfortunately, as good as unknown ;" yet with these he homo- 

 logizes the pores of the sponge. At p. 116, the petaloid 

 arrangement of the vents in AxineVa poh/poides, Sdt. (Spong. 

 Adriatic. 1802, t. vi. f. 4) is regarded by Hiiekel as antimcral 

 or homologous with the segmental divisions of a coral-polype ; 

 and therefore he sets these sponges down as "true Radiata ;" 

 while, in the following paragraph, the fringes round the vents 

 in Osculina iwhjstomella (2nd Suppl. Spong. Adriat. t. i.) are 

 regarded as " incipient tentacles" — after Avhicli Hiiekel observes 

 that whether this be right or wi-ong, it is of " less importance," 

 because the tentacles arc "almost wanting" in Antijmfhes, 

 But considering that these fringed apertures were neither dra^vn 

 nor ever seen by Schmidt himself, and that, as I have shown in 

 CUona coraUinoideSy they belong more to the pore-areas than to 

 the vents, they can hardly be homologized with the tentacles 

 of an Actinia. 



At p. 116 it is also stated that "the conditions of sfocl'- 

 formafion or cormogeng are exactly the same in the corals and 

 the sponges." True ; but the Compound Tunicated animals 

 and the Polyzoa, &c. &c. are grouped together in a similar 

 manner — in " systems." 



Among the calcareous sponges which Hackel tells us he 

 found at Naples, and preserved in spirit, we read, at p. 12, 



