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



of the soft parts. Professor Huxley, who regarded them only 

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

 sicolla punctata, " It is the connecting-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 Thalassicolla 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 

 Orbitoides ;" 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 Holoihuria ; and we 

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



Accordingly, though unprepared to allow that the real con- 

 necting-link between the Foraminifera and the Sponges is to 

 be found in Thalassicolla, 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 with in the Thalassicollidae, but in the 

 Dictyochidse, as has already been shown by me elsewhere f, 

 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 Thalassicolla than in the Foraminifera — there appears 

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

 the two forms in question. 



With reference to the distinction into the. simple and com- 

 posite forms of Thalassicollidae, suggested by ; Midler but re- 

 pudiated by other writers on analogical grounds only, I may 

 mention that isolated free-floating individuals of the Sphcero- 

 zoum and Collosphcera type are constantly to be met with ; 

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

 and have not been separated from the parent matrix by violence 

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

 floating organisms when the composite masses are apparently 

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



* Huxley on Thalassicolla, Annals and Magazine of Natural History, 

 ser. 2. vol. viii. p. 429. 



t See my observations " On the Process of Mineral Deposit in the 

 Rhizopods and Soonges," in the Annals and Magazine of Natural History 

 for January 1864* 



