DEVELOPMENT. 



193 



Patten's results,* the question requires further investigation. 

 According to Patten the mesoblastic layers of the embryo 



C_J V & 



pulsate rhythmically long before the formation of the heart. 

 Patten also states that the blood-corpuscles are partially derived 

 from the wall of the heart. 



Reproductive Organs. In P. orientaHs the reproductive organs 

 are developed as follows : The reproductive glands have a 

 mesoblastic origin. The immature ovaries and testes take the 

 form of elongate oval bodies, which prolong themselves back- 

 wards into a long thin thread-like cord or ligament (figs. 

 114, 115). These lie in the perivisceral space, between the 



Fig. 114. Young Ovary of B, germanica. 

 (Oc. 2, Ob. DD, Zeiss.) 



Fig. 115. Young Testis of B. germanica. 

 (Oc. 2, Ob. DD, Zeiss.) 



somatic and splanchnic layers of the mesoblast, and on the 

 sides of the abdomen. The glands divide tolerably early into 

 chambers, which have, however, a communicating passage (figs. 



* Loc. cit. 



O 



