xliv 
THE VOYAGE OF H.M.S. CHALLENGER. 
Certainly the position, arrangement, and characters of these cells are very suggestive, 
but further observations appear to be necessary before their sensitive function can be 
definitely admitted. 
Protoplasmic Continuity. 
Whether the cells just alluded to should prove to be sesthocytes or not, there remains 
every reason for believing that the collencytes play the part of a rudimentary or 
undifferentiated nervous system, i.e., they serve as intermediaries placing the various 
Pig. IX. — Diagram to represent the protoplasmic continuity of a sponge, ep., epithelium ; oes., sesthocytes ; coll., Collen- 
cytes ; me., myocytes ; flagellated chambers ; y?i., seen from the prosodal face ; JI2., from the aphodal ; fl^., in 
median longitudinal section ; v., velum, seen en face; a transverse section is seen in the middle of the same canal as 
that in which this occurs. 
histological elements of the sponge in protoplasmic continuity. When describing Thenea 
muricata} I was already much impressed with this view and wrote as follows: — “The ends 
of the fibres or of the branches from them (^.e., of the collencytes) appear to be ultimately 
brought into close connection with the ectodermal and endodermal layers, for on the 
inner faces of these layers fine filamentous processes are often seen wandering, and the 
branching processes of the connective-tissue corpuscles (collencytes) can frequently be 
traced right up to them ; in several cases also I believe I have seen a connection between 
the individual cells of a flagellated chamber and the branching processes of a corpuscle. 
^ Ann. and Mag. Nat. Hist., ser. 5, vol. ix. p. 446, 1882. 
