14 PROF. E. A. MTNCHIN' ON THE [May 2, 



all of small size. The big, spreading colonies of contorta always 

 have monaxons. It is my belief that the absence of monaxons is 

 simply a juvenile featui^e, so to speak, of the sponge, and that they 

 are only formed when the sponge has grown to a certain size. 

 Such changes of spiculation with age are probably more frequent 

 in sponges than is usually supposed. For a parallel case I need 

 only refer to Topsent's observations on Cliona celata. 



A point which requires brief discussion, however, is why 

 Lendenfeld fovnid only the sjnnosa-iovva. in the Adriatic, and not the 

 contorta-iovm., if these two forms are really only age- variations in 

 one species. Are we to suppose that in the Adriatic the sponge 

 does not acquire monaxons ? In my opinion the explanation of 

 this point is to be sought in quite a different manner. In his 

 ' Kalkschvvamme der Adria ' [3] Lendenfeld describes another 

 species of Clathrina occurring commonly in the Adriatic, namely 

 C. reticulum. I have also found this species very abundant at 

 Banyuls, and I possess many specimens of it ; but my experience 

 of this species at Banyuls differs sharply in one respect from 

 Lendenf eld's observations upon it in the Adriatic. I find reticulum 

 to be more constant in external form and characters than any 

 other species of Ascon. All the specimens I have seen — and at 

 one time I had some hundreds of specimens, collected in order to 

 obtain the larval development — are compact, rounded, cushion- 

 like masses of slender, closely-knit tubes, forming a dense and 

 finely-meshed reticulum from which arise one or more oscular 

 tubes of much larger calibre than the tubes forming the body of . 

 the sponge. I have figui^ed such a specimen elsewhere (4, p. 6, 

 fig. 6). In short I have never had the slightest difficulty in 

 recognising reticulum at sight, though its spiculation often 

 approaches that of contorta very closely. My astonishment was 

 therefore great to find that Lendenfeld describes this sponge as 

 occurring (at Sebenica and Lessina) in nearly all the forms generally 

 found in Ascons. There is thus a great discrepancy between Len- 

 denf eld's observations and mine with regard to this species, and I am 

 inclined to think that this is to be explained simply by Lenden- 

 feld not having recognised the true contorta, but having confused 

 it with reticulum. This is a supposition which I am unable to 

 prove or test ; but if correct, it would explain why Lendenfeld 

 did not find the true contorta occurring in the Adriatic as well as 

 spinosa, and also why he finds reticulum so variable in form when 

 in my experience it is so extremely constant. I may add, finally, 

 that the figures of monaxons of reticulum given by Lendenfeld 

 (3, pi. viii. figg. 7 6-7/) are more like those of contorta than those 

 of 7-eticidum, though not exactly like those of either, as these 

 sponges are known to me. 



I will now describe some of the historically important specimens 

 to which I have had access, and I begin with the type-specimens 

 of Bowerbank's Leucosolenia contorta in the British Museum 

 (Bowerbank Coll. 988). The " type " consists of seven dried 

 specimens, all very small, stuck on a card. The largest specimen, 



