Prof. M. Schultze on Polytrema rainiaceum. 411 



Carpenter had proved their Foraminiferous nature; but, as 

 sponge-spicules occurred in their chambers. Gray regarded the 

 structures as transitional forms between Foraminifera and 

 Sponges. Gray also met with the Polytrema miniaceum of the 

 Mediterranean, but leaves it doubtful whether this is to be 

 arranged with the Foraminifera or with the Bryozoa near Cri- 

 brillina. He gives it the new name of Pustularia rosea^. 



At Gray^s request, Carpenter then more fully investigated the 

 structures arranged in the genus Carpenteria, and published a 

 memoir upon them in the ' Philosophical Transactions ' for 1860 

 (vol. cl. pp. ^Q^ietseq.), in which he also mentions the Polytrema 

 miniaceum of De Blainville as an organism which possesses a 

 Foraminiferous structure of the calcareous shell, and is most 

 nearly allied to the genus Tinoporus (p. 561). Carpenter found 

 the sponge-spicules constantly in the chambers of the Polytha- 

 lamian named after him, and intimates his adhesion to Gray's 

 view that it is a transition form between Foraminifera and 

 Sponges. 



Whether we regard Sponges as animals or plants, the occur- 

 rence of transition forms between them and the Polythalamia 

 must, under any circumstances, be in the highest degree inter- 

 esting. An organism of the nature of the Rhizopod-body is 

 supposed to produce simultaneously an external calcareous shell 

 and an internal framework of siliceous spicules. The Sponge- 

 structure, the characteristics of which consist in a much higher 

 histological diflPerentiation of the living substance than appears 

 to occur in the Polythalamia, is supposed to pair with the simple 

 protoplasm-body, not divisible into cells, of the calcareous- 

 shelled Rhizopoda. The affair evidently deserved the most 

 thorough consideration and the most careful testing ; there was 

 a fundamental importance attaching to it. For this reason, it 

 was with much pleasure that I found amongst the spirit-speci- 

 mens collected, in the summer of 1861, by Prof, de la Valette, 

 for the Anatomical Museum of this place, a Crab and a tube 

 of Vermetus covered with numerous specimens of the same 

 Polytrema miniaceum which I had previously examined in the 

 dry state. As these specimens contained sponge-spicules and also 

 exhibited the organic contents of the chambers in a very perfect 

 state of preservation, I resolved to make a careful investigation 

 of all the specimens at my disposal, in order to determine whe- 

 ther any facts could be discovered which would show it to be 

 either certain or probable that the calcareous shell with its or- 

 organic contents and the siliceous spicules all three combine to 

 form one organism. 



* Annals, ser. 3. vol. ii. p, 386. 



27* 



