ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 523 



fibrils multiply. The meshes or interstices of the interwoven fibrillar 

 strands are the primary cartilage cavities, which are enlarged by the 

 growth of the pre-chondral and cartilage cells. As the cavities are 

 enlarged, there is a displacement of the fibrils of the framework. This 

 is the first fibrillar stage of the cartilage primordium. 



By the deposition of a .homogeneous cementing substance on the 

 part of the cartilage cells, the matrical fibrils of hyaline cartilage are 

 " masked." The matrix appears homogeneous and becomes basophilous. 

 This is the second basophilous stage of hyaline cartilage. In fibrous 

 cartilage and elastic reticular cartilage there is no " masking " ; they 

 persist histogenetically at the first fibrillar stage of hyaline cartilage. 



Typical cartilage cells are not found in the first stage of histogenesis. 

 They appear in the last stage. Their role is not dear, but they probably 

 form the cementing substance, perhaps also the chondroitin-sulphate. 

 Cell divisions occur only in young, just differentiated cartilage cells. In 

 perichondral chondrogenesis they occur only at the margin of the 

 cartilaginous tissue. These divisions give rise to the cell-territories of 

 the cartilage-matrix, which have nothing to do with the histogenesis of 

 cartilage. They are not seen in bone and ivory. 



Chemistry of Development.*— R. A. Gortner has enquired into the 

 relation between the chemical compounds in trout-eggs, whether they 

 enter the growing tissues in the form in which they are laid down in 

 the egg, or whether there are modified synthetic changes. If not, we 

 must think of the various egg-proteins- ovalbumen, ovomucoid, ovo- 

 globulin, etc. — as containing not only all of the amino-acids necessary 

 for the formation of such complex proteins as haemoglobin, but also that 

 each amino-acid is present in the egg in exactly the quantity which will 

 be needed later by the growing organism. 



His results show that synthetic action does take place, that the 

 simpler mon-amino-acids are in some way transformed into the more 

 complex constituents of the cell nucleus. It was also found that there 

 was a selective utilization of the nitrogen fractions which were " burned " 

 to furnish the energy of development. 



Permeability of the Shell of Selachian Eggs.f — E. Peyrega 

 publishes a preliminary note on experiments on the shell of the dog- 

 fish egg. The embryo is enclosed in a thick firm egg with four 

 clefts, two at each end on opposite sides. In advanced embryos these 

 clefts are widely open, and give easy communication with the exterior, 

 but in the very young stages they are much less wide, and seem entirely 

 closed. Experiment showed that in the young stages the shell itself 

 is permeable by osmosis, both as regards water and salts. The results 

 of the different experiments are given in tabular form. 



* Yearbook Carnegie Inst. Washington for 1913, pp. 106-7. 

 t Bull. Soc. Zool. Prance, xxxix. (1914) pp. 211-14 (3 figs.). 



