72 Mr. G. P. Bidder. 



II. Classification. 



Minchin, in 1896 (20) and 1897 (21), recorded that the larva of 

 L. variabilis is an amphiblastula, as shown by Metschnikoff for 

 L. Lieberkiihnii, ; and that that of the species coriacea, cerebrum, 

 rcticulum, and contorta (sensu Bwk.) is a parenchymula, as shown by 

 Miklucho-Maclay (1) for blanca (confirmed by Minchin), and by 

 Schmidt (2) and Metschnikoff (6) for primordialis and clafhrus. He 

 pointed out that the first spicules to appear in the amphiblastula 

 larva are acerates, in the parenchymula larva triradiates. He found 

 that in L. botryoides, variabilis, complicata, and Lieberkuhnii the 

 nucleus of the collar-cell is distal, as in Sycon in the species with 

 parenchymula larvae it is basal.* 



On these important observations he divides the Homoccela into 

 two families. 



(1) Clathrinidce (Clathrina clathrus, coriacea, cerebrum, reticulum, 

 contorta, and Ascandra falcata) with reticulate external form, equi- 

 angular triradiate systems, collar-cells with basal nuclei, parenchy- 

 mula larva, and triradiates the first spicules to appear. 



(2) Leucosoleniidce (Leucosolenia botryoides, complicata, LieberJcahnii, 

 variabilis, and Ascyssa (?) ) with erect or arborescent form, sagittal 

 triradiate systems, collar-cells with terminal nuclei, amphiblastula 

 larva, and monaxon spicules the first to appear. Such Sycons as 

 S. raphanus he derives from the Leucosoleniidas, but leaves it an open 

 question whether some Heteroccela may not be derived from the 

 Clathrinidae. 



I propose to emphasise very considerably the lines he has indicated, 

 and particularly the suggestion (originally made by Keller (5)) that 

 Leucosolenia is closely allied to the Sycons. The classification of 

 sponges according as they are homoccel or heterocoel, is a physio- 

 logical classification by the most essential and active organ of the 

 sponge ; I have always regarded it as no more satisfactory than 

 classifying higher animals according to whether they walk, swim, or 

 fly. Dendy has already pointed out the close resemblance of his 

 Leucascidas with the reticulate Ascons ((17) pp. 166, 190, 249, &c.) ; 

 I findf that Heteropegma nodus Gordii of Polejaeff has basal nuclei 

 to the collar-cells and that the optic axis is perpendicular to the plane 

 of the triradiates, while Anamivilla is opposed to it in both these 

 characteristics. [I have also confirmed on L. Lieberkuhnii, Minchin's 

 observation as to the distal nuclei in Leucosolenia.'] There is perhaps 



* It may be remembered that I stated to the Society, in 1892, that " the nucleus 

 of Homoccela is generally basal, whereas in the Heteroccela, contrary to current 

 statement, it is almost always distal " (16), p. 479 ; cf. also (19), p. 21. 



f I owe to the kindness of Dr. Vosmaer and Dr. Polejaeff the opportunity of 

 investigating type-slides of the " Challenger " sponges. 



