^iS Mr. Weaver's View o/'Ehrenbei'g's Observations 



in obtaining a clear view of the whole. The assiduous and 

 careful labours of d'Orbigny retain their full value, serving 

 as a basis to all future researches; and if in the present com- 

 munications I shall have succeeded in turning the inquiry into 

 a more physiological channel, my object will be attained. 



To the term Polythalamia, (originally introduced by Dr. 

 Breyn, of Danzig, in 1732,) a different extension or significa- 

 tion under other names has been given by different authors. 

 To remove this unsteadiness and wanton change of names, 

 which only lead to obscurity, it appears advisable to apply the 

 term Polythalamia, in preference, as Soldani had done, to that 

 group in which the animalcules actually live in many cells, and 

 do not, like the Nautili, possess many empty cells. Tliis di- 

 stinction, that the animal of the Polythalamia lias no empty 

 cells, but that all its cells are simultaneously occupied, is of 

 particular importance in their systematic arrangement among 

 other animal bodies. Where tliere are many cells, they con- 

 sist either of so many single animals, the whole constituting a 

 polypary, or of organically filled integrant portions of one 

 and the same individual forming groups. Both structures are 

 foreign to the true Cephalopods. The shell-bearing Cepha- 

 lopods may with Linuccus be divided into the unilocular and 

 muUilocnlar. 



On the other hand, the want of a sipho which has been as- 

 signed as a character of Polythalamia, and from which they ' 

 were named Asiphonoidea by De Haan, is incorrect, inasmuch 

 as many really possess a part which may be fully compared to 

 a sipho, if not in function, yet in form, namely, the tube which 

 connects the separate cells of Nodosarina and of all individual 

 many-celled forms. It is only in the Miliolina family among 

 the simple Polythalamia, and it is only in the families of Aste- 

 rodiscina and Soritiiia among those forming polyparies, that 

 the want of a sipho is really necessary, because they live in- 

 dividually in single cells. But all the Nodosarina, Textula- 

 rina, Uvellina, Ilotalina, and Plicatilia among the simple Po- 

 lythalamia, and the Frumentarina, Plelicosorina, and Alveo- 

 linea among those which form polyparies, possess tubes of 

 connexion between the cells, which very frecjuently resemble 

 also in form the sipho of the Nautilus. D'Orbigny, it is true, 

 states also that the cells of Foraminifers are connected by se- 

 veral openings; that, howevei', proceeds from an erroneous 

 view, for sucli Polythalamia alone present several openings at 

 the border of the cells, whose calcareous surface is interrupted 

 in the form of a net-work, exhibiting often a relation analogous 

 to that which is frequent in Madrepora and Astra^a, in wiiich 

 the soft body is not divided or sharply cut off by com- 



