THE SPONGES. 13 



In the classification of the Hexactinellida the changes introduced by 

 Schulze and Ijima in the system of the former, as laid down in the "Chal- 

 lentJ-er" Report on the Hexactinellida, have been in general adopted, where 

 they concerned the types treated of in this Report. For the Tetractinellida 

 I make use of Sollas's system. Topsent in a recent discussion (1902) pro- 

 poses certain changes in Sollas's treatment of the streptastrose forms, but 

 the changes proposed especially concern the definition of the genera and the 

 two subdivisions, and do not materially alter the classification of the group. 

 Lendenfeld's very extensive changes in the classification of the Asfrophora 

 (1894, 1903) do not seem to me an improvement on the system of Sollas. 

 In dealing with the Monaxonida I employ Topsent's group Hadromerina 

 (1898) and also follow this author (1894 a ) in the division of the Hali- 

 chondrina into families. 



In regard to spicule terminology the usage except in minor particulars 

 and with respect to a few terms has been practically uniform since the 

 " Challenger " Reports. The useful list of Schulze and Lendenfeld (1889) 

 includes terms employed in the "Challenger" Reports and others as well. 

 Some of the latter offer no advantage over the "Challenger" terms, and 

 have not been generally adopted, e.g. ampliiox for oxea., ampliistrongyl for 

 strong yle^ amphittjl for tylote, chelotrop for calthrops. Vosmaer (1902) in a 

 recent paper full of interest discusses some of the forms with regard to 

 which there is not a uniform usage. Prominent among these is the 

 streptasier. Sollas (1888) included under this head a long series of forms, 

 which he divided into plesiasters, metasters, spirasters, amjyJiiasters, and sani- 

 dasters. Of these the first four, and especially the first three, intergrade 

 freely. Vosmaer thinks it impossible to carry out in practice the distinction 

 between plesiasters, metasters, and spirasters, and would designate them all 

 spinispirae, including under this term some at any rate of Sollas's amphi- 

 asters. Schulze and Lendenfeld (1889) use spiraster, amphiaster, and sani- 

 daster in the sense of Sollas, and do not use pksiaster and metaster, but 

 employ the term streptasier for spicules which in Sollas's terminology 

 would fall under these two heads. Lendenfeld (1903, p. 12) continues to 

 use the terms amphiaster and spiraster, but does not employ streptasier, 

 metaster, pksiaster, nor sanidaster. The sanidasters (Sollas) are included under 

 microrhahds (Lendenfeld), e.g. in Trihrachion schmidtii Weltn. The spirasters 

 and metasters of Sollas are together included in spirasters (Lendenf.), e.g. 

 in Pachastrella {Poecillastra) schidsei (Soil.) The pksiastos (Sollas) are passed 



