MATERIALS FOR A MONOGRAPH OF THE ASCONS. 501 



development. Ascandra is similar in all its characters, but 

 has^ the gastral layer folded by reason of the great develop- 

 ment of the gastral rays of the quadriradiates. The genus 

 Leucosolenia, ou the other hand, has an erect or arbores- 

 cent form, sagittal triradiate systems, collar-cells with ter- 

 minal nuclei, amphiblastula larva, and " protascyssa" stage in 

 the development. Of the genus Ascyssa, all that can be said 

 at present is that the skeleton consists entirely of mouaxon 

 spicules. 



My classification has not yet been in the field long enough 

 for it to have received the criticisms which I hope it will call 

 forth. The only point which as yet has been raised is with 

 reference to the name Ascandra. Leudenfeld has raised 

 objections to my retention of this name, coined by Haeckel, in 

 quite a different sense, for the species falcata, one out of the 

 many species which Haeckel referred to this genus. I will 

 not revive the discussion, since Leudenfeld has admitted 

 {' Zool. Centralbl.,' iv. No. 7, p. 231) that the course taken by 

 me was ''vielleicht formal richtig, real aber jedenfalls un- 

 praktisch.'^ If the retention of the name Ascandra is for- 

 mally correct I desire no more, for I am quite of opinion that 

 in a question of nomenclature, which should be treated purely 

 as a matter of names, finality can be attained only by rigid 

 adherence to rule, even if inconvenient.^ 



I propose now to develop my scheme of classification further 

 by dividing the Ascons into two families, corresponding to their 



1 The abstract of my classification given by Lendenfeld (1. c.) misrepresents 

 one point completely. la my diagnosis of Clathrina I gave as one of the 

 characters "principal spicules of the skeleton, equiangular triradiate sys- 

 tems," having previously defined the term "principal spicules" as those "of 

 which the general skeleton is composed, and which are found in all parts of 

 the sponge," as distinguished from spicules forming " a special dermal or 

 other layer restricted to some region of the sponge colony." Lendenfeld 

 cites this point in my diagnosis as " spicules principally equiangular " 

 (Nadeln hauptsiichlich gleichwinkclig), which gives quite a wrong impression. 

 Of Leucosolenia I stated "triradiate systems always sagittal," exception 

 of course being assumed of those abnormal and irregular spicules which are to 

 be found in every specimen. This, again, is quoted as " spicules principally 

 sagittal." 



VOL. 40, PART 4. — NEW SER. N M 



