253 



podia begin to protrude from the vestibular cavity (oral opening) and small 

 papillae appear on their suckers (Figure 197B). The pentactula may reach a 

 length of 1 mm. The dermal plates and skeletal elements of the ambulacral 

 podia begin to form while the pentactula is still in the plankton. Skeletal 

 elements are absent in the primary tentacles. Plates are visible in a live larva 

 at low microscopic magnification when the larva is slightly pressed (Figure 

 I97D, E, F). On settling, the preoral lobe is reduced and the juvenile moves 

 over the substrate using its primary tentacles and two ambulacral podia (Fig- 

 ure 197C). Sometimes juveniles are trapped in bottom catches of plankton. 



FRAUDULENT EUPENTACTA EUPENTACTA ERAUDATRIX 

 (DJAKONOV AND BARANOVA) 



Eggs large, ellipsoidal, dark green, yolky, 400-420 fim in diameter. They are 

 enveloped in a thick jellylike envelope. The blastula forms after 13-15 hrs 

 of development at a water temperature of 20-21 °C. It is greenish and slightly 

 flattened dorsoventrally. 



The gastrula has formed within 24 hrs upon fertilization. Like the blas- 

 tula, it has a greenish tint too, is flattened and uniformly covered with short 

 cilia. Both the blastula and the gastrula swim in the surface water layer, they 

 rotate around their axis with the animal pole directed forward. 



Doliolaria 



This stage develops within two days. It is slightly flattened dorsoven- 

 trally. The oral opening is situated slightly above the equator. The entire 

 doliolaria is uniformly covered with short cilia and tinted green. The preoral 

 lobe forms now and contains the entire nutrient reserve, because of which it 

 is darker than the rest of the larval body. The length of the larva at this stage 

 is 400-450 |im (Figure 1 98 A). 



Pentactula 



This stage is attained after 57 hrs of development. The body is also 

 slightly flattened dorsoventrally and covered with short cilia. As in C. ja- 

 ponica, ciliated bands do not form in this species. In the broadened vestibular 

 cavity the suckers of the five primary tentacles are discernible. At the lower 

 end of the body above the anus lie the two ambulacral podia of the medioventral 

 canal. The length of the larva at this stage is 500 |im (Figure 198B). In the 

 late pentactula the madreporite and plates of the perioral calcite ring are 

 clearly visible. In addition, spicules develop on the dermal plates and two 

 plates of ambulacral podia, which lie in the suckers (Figure 198D, E, F). The 

 skeletal elements can be seen in a live larva at lov/ microscopic magnification 

 and with slight pressing of the larva. On settling, the preoral lobe reduces and 



