744 



THE AMERICAN NATURALIST [Vol. XL 



are open and connect with other spaces in the mesenchyme or con- 

 nective tissue. The differences in method of formation are refer- 

 able to locally different conditions of development and have no 

 important morphological value. 



The endothelium arises at a time when the blood corpuscles are 

 in circulation in connection with lacunae, the schizoccele, in the 

 connective tissue and is to be regarded as arising phylogenetically 

 from a lacunar system bounded by connective tissue whose physi- 

 ologically most important and hence earliest differentiated portion 

 lay in the region of the gut. 



The localization of the blood and vascular forming cells in the 

 region of the mesenteries confirms the view of Lang, founded on 

 comparative anatomy, that the first differentiation of the intestinal 

 blood sinus of the Coelomata occurred in the separation of vessels in 

 the region of the dorsal and ventral mesenteries. 



The blood corpuscles are to be regarded as 'swimming mesen- 

 chyme cells' in Ziegler's sense. They arise in the medio- ventral 

 mesoderm region. 



J. S. K. 



BOTANY 



was issued on February 2()th. It brings the total pagination for the 

 quarto volume up to 982 and the plates to 31; and in addition to the 

 conclusion of the list of species contains an analysis of orders and 

 families, a list of collectors, with bibliography, an account of the 



Vol. 4 of Kciclu 's F/uni (Ir Chile completes the Compositte and 

 contains correction sheets for the first four volumes. 



A third "Contribution to the Flora of the Bahama Islands," by 

 Britton, is separately issued from vol. 4 of the Bulletin of the New 

 York Botanical Garden, under date of March 19. 



