86 



EMBRYOLOGY 



the skeletogenous layer of the Pennatalidae, but which is 

 said by Wilson to arise from the entoderm. 



At an early period the budding of the daughter individuals 

 begins ; these are formed strictly in pairs on the dorsal side 

 of the axial individual (Fig. 37 A, p^). The second pair of 

 polyp buds arises immediately behind the two first ones, 

 the third pair in front of and somewhat ventrad from the 



Fig. 39.— Young colony of Pennatula phosphorea (after Jungersen). A, youngest 

 stage, seen from the right ; B, older stage, from the ventral side ; C, the same, 

 Irom the dorsal side ; j), terminal polyp ; z, terminal zooid ; p^, pi, polyps of the 

 first pinnate leaflet ; p2, p2, polyps of the second pinnate leaflet, etc. 



first pair, the fourth pair in the angles between the third 

 pair and the axial polyp (Fig. 37 B, p^, p^, p^, p^). The buds 

 arise separately at first, but subsequently their basal parts 

 fuse. The individuals that have arisen in this way very 

 soon assume a radial position ; and since the buds that appear 

 later are formed in alternating positions and ventrad to 

 those first formed, and since in the further course of de- 

 velopment they grow so actively that they project beyond 



