354 PROF. E. A. MINCHIN OX 'nVE BRITISII [Dec. 13, 



many, perhaps the majority, of his specific names becoming 

 synonyms. 



There is, however, a further blemish on Haeckel's work, which 

 has been the cause of all the universal confusion in the nomen- 

 clature of these sponges. Haeckel took no notice in his final 

 monograph * of any generic names for calcareovis sponges tised 

 before him. Making a clean sweep of all previous names, he set 

 up twenty-one new genera, seven of which were Ascons. Such 

 11 proceeding could not, of course, be tolerated, being a flagrant 

 violation of the rules of taxonomic nomenclature which have 

 long been followed in this country, and now are universally ac- 

 cepted abroad also. Hence Haeckel's system has undergone 

 various modifications at the hands of subsequent writers. 



The first work of primary importance dealing with calcareous 

 sponges after Haeckel was Polejaeff [18], who i^everted to Bower- 

 bank's use of the name Leucosolenia to denote all Ascons. In 

 works of later date some systematists have followed Polejaefi^ in 

 the use of the name Leucosolenia, as, for example, Topsent ; 

 others have used modifications of Haeckel's system, as, for example, 

 Lendenfeld ; and others, again, have used Leucosolenia in some 

 special sense, as, for example, Breitfuss. In 1896 [15] I put 

 forward a scheme of classification for Ascons which has not been 

 followed by subsequent -writers, but to which I still adhei-e. It 

 would be foi'eign to the purpose of the present memoir to discuss 

 the classification of Ascons genei-ally, but in order to justify my 

 use of the name Leucosolenia I put forward three propositions : — 



(1) That the oldest Ascon genus, Leucosolenia Bower bank, is a 

 valid genus, founded in a perfectly correct manner, its type 

 species being L. hotryoides, the oldest desciibed species of Ascon. 



(2) That therefore the generic name Leucosolenia has priority 

 over all others for this species, and the combination Leucosolenia 

 hotryoides is one that should never be disturbed. 



(3) That therefore in any scheme of classification in which 

 other Ascons are placed in the same genus as hotryoides, they also 

 should be termed Leucosolenia. 



If these three propositions are accepted, it becomes of extreme 

 impoi'tance to describe accurately the specific characters of Leuco- 

 solenia hotryoides. I think I may claim to have done so in the 

 present paper, and from the description below it will be imme- 

 diately apparent that the restriction of the name Leucosolenia to 

 Ascons without monaxon spicules, as done by Breitfuss, is a,n 

 erroi', caused by Haeckel's incorrect description of the species 

 hotryoides. 



As regards the specific determination of Asoons, the chief 

 criticism which I have to make, with regard both to Haeckel and 

 to post-Haeckelian systematists generally, is that sufficient account 

 is not taken in their descriptions of the gi-eat variability of the 



* In Haeckel's ' Prodromus ' [12] he put forward a scheme of classification in 

 which previous generic names were used, but in his ' Monographie ' [13] he com- 

 pletely altered both his classification and his nomenclature. 



