112 RECORDS 



tal plate develops continuously from bone which appears be- 

 neath the perichondrium of the cartilaginous ribs. No part 

 of either the costal plates or of the neurals arises in the 

 skin. While accepting Goette's results as established, the 

 speaker did not accept his conclusion. Neither did he accept 

 the other view that the costals and neurals are composed of 

 dermal bones united with those of the internal skeleton. The 

 speaker held that there were originally three strata of bones 

 on the dorsal surface of turtles. One of these was in the skin, 

 and is represented by the mosaic found in the skin of Derrno- 

 chelys. Another layer was sub-dermal, and this united with 

 elements of the third stratum, namely the ribs and neural 

 arches. The union has become so complete that the bones 

 arise from the same centres. These three strata of bones on 

 the dorsal surface correspond to those which are found in the 

 ventral wall of the Caiman, viz., true ribs, ''abdominal ribs," 

 and bony dermal scutes. 



Mr. M. A. Bigelow compared the germ-layers of various 

 Crustacea with especial reference to the Cirriped Lepas. It 

 was pointed out that in the cleavage leading to the segregation 

 of the germ-layers there are very many resemblances between 

 Lepas and other Entomostraca. Lcpas resembles most other 

 Crustacea with respect to the position of the blastopore, and 

 the extension of the entoblast and mesoblast from that region 

 as a starting point. In Lepas, as in most other Crustacea, the 

 mesoblast and entoblast originate from cells which, speaking in 

 general terms, at first lie in the blastoderm and later migrate 

 into the cleavage cavity. But among these immigrating mes- 

 entoblastic cells one can distinguish the individual cells of ento- 

 blast and two varieties of mesoblast — entomesoblast and ecto- 

 blast. There are observations indicating that similar conditions 

 exist in other Crustacea. 



Henry E. Crampton, 



Secretary. 



