3 

 probal ■•;./ hour thereafter, 



o'cloc - : are to "be found in stages of 



to sixteen LIS. four to six 



since 

 elapse before t ;in to segment, A it takes this long for 



gBBm disc to form on eggs in is 



id one- fourth hours for the Herring (Prook ' 



twelve to thirteen in in ' 



■ ■-.r- Celled Stage. 

 . t, PI, I. is : tormal four-c Lasto- 



derm. The second furrow is horizc crosses the first 



approximately at right angles. Thus there is formed a four- 

 celled symmetrical blastoderm. Sections of this would in 

 no wise differ from those foi , o-celled stages, save in the 

 plane a--b where the beginnings of the segmentation cavity 

 and the periblast would be found. Such a section is not at 



hand unfortunately . 



. . , Pi, I., a more common fori.,, shows slight in- 

 equalities in the size of its blastomeres. Such in 

 ities become more pronounced until they result in renifoj 

 blastodei- ,6 , PI. I. 'i .- , PI. II. is a nea 



horizontal section thro . : of such^for... as Fi| .4 , 



PI, I, i ?a .o of the cells is an arte- 



fact. ,1 interest are trie segmentation cavity i 



