310 DR. G. P. BIDDER ON 



hand, a parasitic or symbiotic spherical cell, containing a greenish-yellow 

 and a red pigment, has been found in the mesoglcea of two Clathrinidce, one 

 at Naples and one in the Chagos Archipelago, and is frequent in Hircinia. 

 The whole cell is of nucleoid (but not nuclear) character, in a cell-wall which 

 resists caustic potash ; it multiplies by binary fission, the daughter-cells 

 separating completely. The cells before division are of the same diameter as 

 the multicellular spheres of Syncrypta spongiarum, and contain pyrenoids. 



The only indication of transition in the mesogloea between Urban's dividing 

 but separating spheres and Vosmaer's coherent colony of 1G spherules, is 

 Vosmaer's statement (p. 412j that he can vouch for the truth of Polejaeff's 

 description (1882) of the " spermaklumpen " arising from the binary division 

 of a spherical cell in the mesogloea. The context, however, rather suggests 

 that this means merely that Vosmaer had inspected Polejaeff's preparations ; 

 and as these are in the possession of Professor Dendy, I leave the discussion 

 of them to him. It is interesting, in connection with the parasitic cells of 

 Hircinia, to note that Polejaeff remarks in another paper (1883, p. 33) on 

 the strange similarity between the spermospores of Keratosa and those of 

 Leucosolenia and Sycon raphanus. It is more remarkable in his monograph on 

 Keratosa (1884, p. 72) to find that Verongia has " spermospores," like Sycon, 

 with a covering cell, but Carteriospongia ' ; sperm-balls," like Oscarella, in 

 endothelial cavities as described by Schulze. The " spermospores " are 8 /u- 

 to 10/i in diameter, shrunk away (?) from the " covering-cell," -which is 

 14 fi to 16 jj, in diameter ; but the " spermospore " shows up to 90 black 

 dots — indicating some 150 if it be a hollow sphere. (Note D, p. 319.) 



Haeckel's " Samenballen " (1872, Taf. 48. fig. 8) measure 20 and 27 /x 

 across, but no later author describes any object of similar appearance. 



Dendy's fig. 87 shows, in my opinion, a pylocyte in which a 16-cell sphere 

 has jammed. It must not be inferred from this that only monads can enter 

 the flagellate chamber. Fig. F shows a pylocyte from Sycon raphanus widely 

 open and choked with starch grains. The sponge was killed after 5 minutes' 

 feeding; it will be seen that its diameters are 12 p, X 10 /x. In Grantia 

 compressa (fig. Gr) the pylocytes are almost exactly the same size — from 10 to 

 13 p in diameter. There is, therefore, room for the 7 p spheres to pass, and 

 it seems certain that those in the chambers of this sponge have so passed. 

 Dendy writes (1914, p. 324) : — "I have found them, not only in the chambers, 

 but also adhering to the outer surface of the sponge and in the inhalant 

 canals, though, except in the chambers themselves, only in very small 

 numbers. I have also found some evidence of their breaking up into sperma- 

 tozoa " [i.e. monads] "in an inhalant canal." 



Syncrypta spongiarum, therefore, reaches and enters G. compressa as 16-, 

 8-, and occasionally 4-celled spheres, the first of which presumably break up 

 into the isolated monads that are also found in the flagellate chambers, where 



