of the Sponges to the Corals. 2^ 



development of Spongillaj he would not have given a prefer- 

 ence to the Calcispongige for this purpose. 



It is remarkable that Hackel, with the exception of stating at 

 p. Ill that " the simple and extremely significant fact that the 

 reproductive cells are produced, by division of labour, from 

 the nutrient vibratile cells of the entoderm or vegetative germ- 

 lamella applies to the sponges equally with the Acalephs," 

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

 sponge-structiu'e is built up and sustained. Such an omission 

 could never have occurred with an observant, sagacious mind 

 like his, ardent in the pursuit of truth, had he added to his 

 indefatigable researches on the calcareous sponges a study of 

 the development of Spongilla, such as I have described, or 

 even had he experimented after a like manner on the living 

 calcareous sponges. 



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

 which he has given the names of Clistosyca and Cophosyca, 

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

 regarded as retromorphosed forms, related to the others 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 Axinella 'polypoides, Sdt. (Spong. 

 Adriatic. 1862, t. vi. f. 4) is regarded by Hackel as antimeral 

 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 Oscidina polystomella (2nd Suppl. Spong. Adriat. t. i.) are 

 regarded as " incipient tentacles" — after which Hackel observes 

 that whether this be right or wrong, it is of " less importance," 

 because the tentacles are "almost wanting" in Antipathes. 

 But considering that these fringed apertm-es wei'e neither drawn 

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

 Cliona corallinoicles, 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 stock- 

 formation or cormogeny 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, 



