inner wall splits open an-i tin- in-n.wth of' cells [.asses out and ventral 

 to the medulla as the sclerotome or anlage of the vertebra. The split 

 becomes the intervertebral cleft or foramen. As the myotome gives 

 rise directly to the sclerotome there is no secondary segmentation of 

 the vertebral column, but rather a proximal dislocation of each 

 sclerotome by the length of half a myotome. After this ske!etegem>us 

 material has left the myotome its walls give rise t<> muscles; the inner 

 wall first, forming the dorsal part of the lateral musculature ; the outer 

 wall, in man, growing ventrally to furnish muscles for the ventral 

 body wall, digestive tract and also the limbs. The muscles in the 

 limbs are formed from several myotomes, are representations oi several 

 metameres, moreover all the segmentation seen in the ventral region 

 and in the limbs is not formed from the lateral plate, but in the above 

 outgrowth into them of parts of the axial myotomes. These muscle 

 buds growing into the limb surround the axial anlage of the future 

 skeleton. 



Sections ofthe embryo of 2-5 mm. with 13 somite,, shou a marked 

 modification of the ectoblast near the intermediate cell mass, becoming 

 a cellular ingrowth posteriorly in older embryos. This is regarded by 

 the author as undoubtedly an ectodermal component of the Wolffian 



ENTOMOLOGY.' 

 Descriptions of New North American Bees.— The follow 

 ing species of Halidm have the head and thorax and sot 

 abdomen, greenish or bluish, the surface of mewthoraa 

 roughened, except in 5, and with a distinct puJ 

 with few long teeth; and are arranged according to - 

 with the largest. The following synopsis may aid in separating them 



Mesothorax coarsely reticulated on the sides ; 



Head greenish, thorax bluish, legs dark, ] ■ ™**T* J? 



Head and thorax bluish, legs mostly yellow, 



Mesothorax punctured, not reticulated ; 



Head, thorax and abdomen greenish ; 



Pubescence of abdomen yellowish, thin, not con- 



ceahng surface, J 



