720 PROF. A. DENDY AND MR, R. W. H. ROW ON 



basal stolon as in L, lucasi and L. stolonifer, to complex reticulate 

 colonies which have acquired by integration a new individuality 

 of a higher type, sometimes with pseudogaster, pseudosculum, 

 pseudoderm and pseudopores, as in L. ventricosa, and sometimes 

 with reversal of the canal system as in L. cavata. It may happen 

 that one and the same colony exhibits a reticulate structure in 

 one portion, and a non-reticulate in another, as in several forms 

 figured by Haeckel [1872]. For further information as to the 

 variations in the mode of colony formation the reader is referred 

 toDendy [1891 A]. 



Haeckel's Ascandra fcdcata, which we include in the genus 

 LeuGosolenia, has been made by both Minchin [1896] and von 

 Lendenfeld [1891] the type of a special genus (with the generic 

 names of Ascandra and Homandra i-espectively) on account of 

 the peculiar appearance of the gastral layer, which is thrown into 

 folds in such a way that in transverse section there appear to be 

 present a series of shallow radial tubes. These endodermal ridges 

 are always supported by the large apical rays of the gasti-al 

 quadriradiates, which have either pushed the layer of collared 

 cells out before them as they grow, or formed a foundation upon 

 which the collared cells have spread. It may be pointed out that 

 other Homocoelidje also show this type of structure, e.g. L. canar- 

 iensis and L. gegenbauri. We ourselves do not consider that this 

 character is of sufficient importance, per se, to take generic rank ; 

 nor do we consider that there is any relationship between the 

 " pseudoradial " character thus given to the gastral layer, and a 

 true syconoid canal system, since, in the radial tubes of Sycon, for 

 example, both dermal and gastral layers are folded, while in 

 Leucosolenia falcata the gastral layer only is a fleeted. Further, 

 embryology shows that the radial tubes of Sycon are outgrowths 

 from the central gastral cavity, and not formed by ingrowths 

 into it. Had the syconoid type of canal system originated from 

 some such condition as that of Leucosolenia (Ascandra) falcata, 

 the sycon person would have been provided with a dermal cortex 

 ab initio, whereas the more primitive Sycettid^e have the ends 

 of the chambers freely projecting on the surface of the sponge. 



The position of the nucleus of the collared cells in this genus 

 is not, so far as we are aware, correlated with any particular 

 type of spiculation or canal system, and we cannot, if only for 

 practical reasons, make use of this character by itself for sub- 

 dividing the genus. As a means of grouping the various species 

 of the genus into sections, however, we may, as in the higher 

 forms, adopt the criterion afibrded by the presence or absence of 

 oxea. 



We recognise the following species as belonging to this 

 genus : — 



Section A. Oxea present. 



1. L. AMCEBOiDES Hacckel. 



Ascandra complicata, var. amcehoides Haeckel [1872]. 



