Dr. W. B. Carpenter on the Polytremata. 881 



types of Foraminiferal structure which are presented in Poly- 

 trema * and Carpenteria f, I should be able to give an ex- 

 haustive account of their structure and affinities. Mj speci- 

 mens were then few in number, and were derived from a 

 limited set of sources. And while I had not at that time 

 recognized the presence of sponge-spicules either in the canals, 

 chambers, or solid skeleton of Polytrema^ I had found the 

 chambers of every specimen of Carjyenteria which I had then 

 examined to be so universally pervaded by them, that I was 

 disposed to agree with Dr. J. E. Gray in the idea that they 

 properly belonged to the organism, which might thus be 

 regarded as a connecting link between Foraminifera and 

 Sponges, — this probability appearing to be strengthened by 

 the curious resemblance in form which the conical Carpenteria^ 

 with its apical orifice, bears to the papilla of a Sponge with 

 its terminal oscule. This suggestion, however, I put forth 

 (as Mr. Carter truly says) with a certain reserve ; and I held 

 myself quite open to modify or withdraw it, as further evidence 

 might indicate J. Prof. Max Schlutze's paper of 1863 showed 

 me that there was a closer affinity between Polytrema and 

 Carpenteria than I had originally supposed. And the subse- 

 quent examination of a considerable number of specimens of 

 both types which have come into my hands from various 

 sources, has satisfied me on the following points : — 



1. That the polymorphism of Polytrema is much greater 

 than I was originally aware of, and that what Mr. Carter terms 

 the " cavernous dilatations " of the interior, which I had only 

 recognized as canals traversing the solid fabric, are often 



* ' Introduction to the Study of the Foraminifera,' 18G2, p. 235. 



t Philosophical Transactions, 1800, p. 504; and 'Introduction,' p. 180. 



\ This is explicitly stated in my original description of Carpenteria 

 (Phil, Trans. 1800). After referring to the opinion of Mr. Cuming and 

 other experienced conchologists that the organisms in question belong to 

 the sessile Cirripeds, I thus continue : — " Their true nature was first 

 suspected by Dr. J. E. Gray, who was led by his study of them to con- 

 sider them as the testaceous envelopes of a Rhizopod intermediate between 

 Spmiges and Foraminifera ; the grounds on which lie came to this con- 

 clusion being, that he found the shell to be raultilocular and minutely 

 foraminated lake that of certain Foraminifera, whilst the fleshy substance 

 occupying its chambers is strengthened with spicules like those of Sponges. 

 Hence he considered this organism in the light of a Sponge enveloped 

 in a shelly case with a single terminal oscule. My opinion as to its 

 character having been asked by Dr. Gray, I soon found reason to agree 

 with him in his general idea of its affinities ; the structure of the shell 

 being most characteristically /wz-u/nmi/eroMS, whilst the substance occupy- 

 ing its chambers is no les.s characteristically spo?if/eotis. In communicating 

 this result, however, to Dr. Gray, I thought it right to suggest the possi- 

 bility that this spongeous substance might be parasitic ; the tendency of 

 certain Sponges to find their way into very minute fissures and passages 



