384 PROF. E. A. MINCHIN ON THE BRITISH [DeC. 13, 



Leuconia somesii; why he should have called these specimens 

 Leuconia is a mystery to me. 



Haeckel gave the species the name variabilis on account of "thd 

 unlimited changeableness of its form as a whole, as well as of its 

 specific skeleton-structure." I have already expressed my opinion 

 upon Haeckel's figiu-es of the external form ; as regards the spicu- 

 lation, L. variabilis is variable certainly, but not moie so than othei- 

 Ascons. The frequent association, mentioned above, of this species 

 with a heterocoele sponge, and the constant contamination, so to 

 speak, of spicvile-prepaiutions of the Ascon by spicules not properly 

 belonging to it, may account for Haeckel's noticing in this instance 

 the variability of the spiculation. 



Haeckel described variabilis as having two kinds of monaxons, 

 small and large ; but from his figure it is evident that the smaller 

 kind seen by him were the small curved monaxons, and he did not 

 notice that they are connected by every possible gradation of size 

 with the large ones. He oveilooked the small straight monaxons, 

 as I must also confess to have done till quite recently. Haeckel 

 made four specific varieties — cervicornis, confervicola, arachnoides, 

 and Mspidissima, — based on variations of the relative numbers of 

 the difierent sorts of spicules, and leading up to his so-called 

 " connexive varieties," distinguished, in his usual way, by ringing 

 the changes on the generic name, such as Ascaltis, Ascortis, 

 Ascuhnis, or Ascyssa variabilis. None of these varieties appears 

 to me to have any taxonomic value except hispidissima, which 

 might be retained for forms such as were named by Bowerbank 

 Leuconia somesii : i. e. for those in which the monaxons are 

 excessively developed in size and number to form a furry pro- 

 tective covering. In my specimens from Roscoff, even from the 

 same rock, I find some which, viewed with a lens, appear smooth, 

 others which appear hispid ; the difference between them is 

 merely one of the length attained by the monaxons (compare 

 figg. 10-13, text-fig. 94, p. 377). The same is true of L. complicata, 

 and there can be no doubt that these sponges respond readily in 

 this manner to differences in their surroundings. 



Of other species of Ascons in Haeckel's monograph, I feel no 

 doubt whatever that his Ascortis coraUorhiza is founded on 

 a specimen of this species with rather large and thick spicules 

 (compare figg. 15 a-15/, text-fig. 95, p. 379). Here also we have 

 a connexive variety, Ascandra corallorrhiza, mentioned. 



Systematists subsequent to Haeckel have for the most part 

 recognized and identified this sponge correctly. A specimen, 

 however, in the British Museum from Trieste, labelled L. varia- 

 bilis, is certainly not this species. L. variabilis does not, to the 

 best of my belief, occur in the Mediterranean ; but it is impossible, 

 I repeat, to make definite statements about the distribution of 

 Ascons in the present confused state of their nomenclature *. 



* Kirkpatrick, in 1901 (Brit. Mus. Rep. ' Southern Cross ' Collections, p. 317), 

 identified an Antarctic sponge as i. variabilis ; but having been able, by the author's 

 kindness, to examine the specimen I am in a position to state that it is not L. varia- 

 bilis but a species, apparently new, allied to L. complicata. 



