86 



EMBRYOLOGY 



the skeletogenous layer of the Pennatulidse, 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 Ä, 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 Jungerseh). ^.youngest 

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

 from the dorsal side; p, terminal polyp; z, terminal zooid ; p^ p', polyps of the 

 first pinnate leaflet ; p-, p^, 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 



