114 THE CANADIAN NATURALIST. [April 



to add to Dr. Dawson's description. The evidence afforded by 

 their internal casts concurs with that of sections, in showing that 

 the segments of the sarcode-body, by whose aggregation each layer 

 was constituted, were but very incompletely divided by shelly par- 

 titions ; this incomplete separation (as Dr. Dawson has pointed out) 

 having its parallel in that of the secondary chambers in Carpen- 

 teria. But I have occasionally met with instances in which the 

 separation of the chambers has been as complete as it is in Foramin- 

 ifera generally ; and the communication between them is then 

 established by several narrow passages exactly corresponding 

 with those which I have described and figured in Cycloclypeus* 

 The mode in which each successive layer originates from the 

 one which had preceded it, is a question to which my attention 

 has been a good deal directed ; but T do not as yet feel confident 

 that I have been able to elucidate it completely. There is certainly 

 no regular system of apertures for the passage of stolons giving 

 origin to new segments, such as are found in all ordinary Polytha- 

 lamous Foraminifera, whether their type of growth be rectilinear, 

 spiral, or cyclical; and I am disposed to believe that where one 

 layer is separated from another by nothing else than the proper 

 walls of the chambers, — which, as I shall presently show, are tra- 

 versed by multitudes of minute tubuli giving passage to pseudo- 

 podia, — the coalescence of these pseudopodia on the external surface 

 would suffice to lay the foundation of a new layer of sarcodic seg- 

 ments. But where an intermediate or supplemental skeleton, con- 

 sisting of a thick layer of solid calcareous shell, has been deposited 

 between two successive layers, it is obvious that the animal body 

 contained in the lower layer of chambers must be completely cut 

 off from that which occupies the upper, unless some special pro- 

 vision exist for their mutual communication. Such a provision I 

 believe to have been made by the extension of bands of sarcode, 

 through canals left in the intermediate skeleton, from the lower to 

 the upper tier of chambers. For in such sections as happen to 

 have traversed thick deposits of the intermediate skeleton, there 

 are generally found passages distinguished from those of the ordi- 

 dary canal-system by their broad flat form, their great trans- 

 verse diameter, and their non-ramification. One of these passages 

 I have distinctly traced to a chamber, with the cavity of which it 

 communicated through two or three apertures in its proper wall 



* Op. cit., p. 294. 



