12 Mr. H. J. Carter on the " Collar " 



baljly by the intercellular protoplasm, to which I shall allude 

 hereafter, that the Sponges, like the Myxogastres, chiefly ex- 

 cavate and work (how?) their way through hard bodies.) 

 This tentacular form of pseudopodium, which is characte- 

 ristic of the Acinetina, I have also witnessed twice, in two 

 cells of Grantia comjyressa, viz. one where the collar had 

 partly become transformed into a pseudo]jodial extension and 

 had caught an unciliated monadine cell (PI. II. fig. 17), and 

 the other where the margin of the collar itself had seized a 

 monociliated one (fig. 18). As these two instances presented 

 themselves during a very short and limited examination of 

 the sponge-cells of Grantia compressa in the way above 

 stated, it is not improbable that they are of very frequent oc- 

 currence. At the same time it should be remembered that 

 many phenomena of this kind are witnessed under the glass 

 cover, from the Infusoria being brought so closely together, 

 which might not occur so frequently in their natural element, 

 where they are ujiconfined and have plenty of room to avoid 

 each other. 



As an instance of a Rhizopod being able to put forth ^'ibra- 

 tile cilia at one time, and replace them b} pseudopodial tenta- 

 cles at another, I, long since, described and figured Podajphrya 

 fixa in the 'Annals ' (vol. xv. p. 287, pi. 12. fig. 10). 



To this it may be added that Prof. James-Clark in no part 

 states that any of his collared flagellated Infusoria possess a 

 polymorphic power over the whole body like the sponge-cell. 



Nevertheless this sagacious observer states (p. 20), regard- 

 ing " the theory of Carter as to the alliance of Sponges with 

 Rhizopods," " my firm conviction" is " that the true ciliated 

 Sj)otiffi(e are not Rhizojmda in any sense whatever, nor even 

 closely related to them, but are genuine compound Jlagellate 

 Protozoa, and are most intimately allied to such genera as 

 Monas, Bicosoeca, Codonosca, Codosiga, and Salpingoecay 



Thus having stated our views respectively on this point, I 

 must leave the reader to judge for himself. 



Contracting vesicles and a nucleus are common to all the 

 sponge-cells, and the former common to the })rotoplasm to 

 which I have just alluded, viz. that which binds them and the 

 whole elements of which the sponge is composed together. 

 The latter is figured and described in one of my earliest papers 

 on SpongiUa (Annals, Aug. 1849, vol. iv. pp. 86-91, pi. 4. 

 fig. 2), wherein it is stated, at p. 81, that, '' when the fleshy 

 mass is examined by the aid of a microscope, it is found to be 

 composed of a number of cells imbedded in and held together 

 by an intercellular substance," and, at p. 91, that "it (this 

 substance) is extended into digital prolongations precisely 



