100 Dr. G. C. Wallich on the Tlialassicollida. 



of tlie soft parts. Professor Huxley, who regarded tliem onlj 

 as "varieties" one of the other, says, with reference to Thalas- 

 sicolla imnctata^ " It is the connceting-link between the 

 Sponges and the Foraminifera. Allied to the former by its 

 texture, and by the peculiar spicula scattered through the 

 substance of some of its varieties, it is equally connected with 

 the latter by the perforated shell of the other kinds. If it be 

 supposed that a ThalassicoUa becomes flattened out, and that 

 a deposit takes place not only round the cells, but between the 

 partitions of the central ' vacuole,' it becomes essentially an 

 Orhitoides)'''' whilst in a note from Dr. Carpenter, appended 

 to the above observations, it is stated that " the cullender-like 

 skeleton of certain Foraminifera is extremely like in its 

 appearance to a fragment of the shell of an Echinus^ or to the 

 plates contained in the integument of a HolotJmria ; and we 

 know that these begin with a network of spicules " *. 



Accordingly, though unprepared to alloAV that the real con- 

 necting-link betAveen tlie Foraminifera and the Sponges is to 

 be found in ThalassicoUa, or that the modification in form or 

 the superaddition of a deposit as described would render it 

 conformable to the type of any of the Foraminifera — in the first 

 instance, because the mode of siliceous deposit characteristic of 

 the Sponges is not met Avith in the Thalassicollidse, but in the 

 Dictyochida3, as has already been shoAvn by me elseAvheref, 

 and, in the second, because the presence of a nucleus, and the 

 much more highly differentiated condition of the rest of the 

 sarcode-substance, attests the existence of a more advanced 

 type in ThalassicoUa than in the Foraminifera — there appears 

 to me to be no sufficient reason for the generic separation of 

 the tAvo forms in question. 



With reference to the distinction into the simple and com- 

 posite forms of Thalassicollidce, suggested by Miiller but re- 

 pudiated by other Avriters on analogical grounds only, I may 

 mention that isolated free-floating individuals of the Sphcero- 

 zoum and CoUosphcera type are constantly to be met AA'ith ; 

 and it is quite evident that these are in a normal condition, 

 and haA^e not been separated from the parent matrix by A'iolcnce 

 during capture, inasmuch as they are to be found not only as free- 

 floating organisms Avlien the composite masses are apparently 

 altogether absent at the surface of the ocean, but also Avithin 



* Huxley oil ThiilaiisicoUa, Auiiak and Mag"azino of Xatural History, 

 ssr. 2. \'ol. viii. p. 420. 



t See my oLservations " On the Process of Miuoral Depo.^it in the 

 Rhiznpods and Sponges/' in the Annab and Magazine of Natural History 

 for Ja:niarA- 18i;4. 



