66 



EMBRYOLOGY 



three smaller ones arranged symmetrically were to be noticed. The 

 Katarife are characterized by the possession of a sail which stands ver- 

 tically on the upper surface of the elliptical disc, and the base of which 

 originally occupies the direction of the long axis of the disc, so that in 

 general the Kataria; possess a biradial structure. It is only in subse- 

 quent stages that the amphitectal (klinoradial) fundamental form of the 

 Vellelida3 is brought out by the sail turning at an angle of forty-five 

 degrees to the above-mentioned axis, so that it stands diagonally. 



We have still to acid something' 

 on the laws of grow^th of Sipho- 

 nophore stocks. In those forms 

 w^hich are charactei-ized by an 

 elongated stem, the different indi- 

 viduals do not bud on the entire 

 circumference, but only along a 

 longitudinal line (Fig. 28). Since 

 the w^all of the stem exhibits a 

 different structure along this line, 

 a cross-section of the stem pre- 

 sents a bilaterally symmetrical 

 arrangement. That side of the 

 stem from which the individuals 

 bud is known as the ventral side 

 (Claus). The fact that the indi- 

 / ^ / \ "(^ viduals of the stem appear to be 



oriented in various directions re- 

 sults from a spiral twisting of the 

 stem, by which, for example, the 

 bisei'ial or multiserial arrange- 

 ment of the nectocalyces on the 

 nectosome is brought about. It 

 was shown by Claus (No. 62) 

 that in the Physophoridae the 

 spiral twisting of the nectosome takes place in the opposite 

 direction to that of the lower portion of the stem. 



As appears from Fig. 28, a budding point for the indi- 

 viduals of the nectosome is found at the upper end of the 

 stem. Another budding point, at the base of the necto- 

 some, supplies in general the buds for the rows of individuals 

 of the stem. Accordingly those groups of individuals which 



Fio. 28. — Young Agalmoyisis 

 (after Gegenbaue). a, stem; b, 

 pneumatophore ; c, only polypite 

 developed ; d, buds of tentacles 

 and dactylozröids belonging to 

 the group of individuals of the 

 first polypite ; e, hydrophillium ; 

 g, buds (nectocalyces) of the nec- 

 tosome ; h, buds of the lower 

 portion of the stem. 



