At that time the digestive system has grown considerably but 

 the intestine still has a sac -like fornn. At this stage of the division the 

 sizes of the pharynx are about 0.017 - 0.012 mm, i.e., considerably 

 larger than among the free -swimming larvae even though the dimensions 

 of the worm are still approximately equal those of the larva. As was 

 described before, the edge hooks do not grow but remain about 0. 008 - 

 0.011 mm in length. The middle hooks have the following lengths: the 

 first pair about 0.03 mm, the second 0. 02 mm, the middle connecting 

 plate 0, 012 - 0. 014 mm, and the lateral, paired 0. 008 - 0. 01 mm in 

 length. The further development of the attaching armature proceeds 

 rather intensively. It is characterized by a rapid growth of middle hooks 

 and of the connecting plates which acquire their difinitive shape and sizes 

 (Fig. 187, A) before the beginning of the formation of the attaching plates 

 on the disc. The growth of the middle hooks proceeds as among all pre- 

 ceding species by way of the accretion of the end which is opposite to the 

 point. The connecting plates increase mainly by way of growth on both 

 ends, at the same time they thicken throughout their lengths (Fig. 187, B). 



The following stage of development is characterized by the 

 formation of both supplementary discs (Fig. 188). They are incepted 

 simultaneously on the dorsal ajid ventral side and at first are hardly 



p. 170 



Fig. 188. Lamellodiscus elegans Bychowsky, young worms from the gills 

 of Sargus annularis from the region of Karadaga (Black Sea); stages of the 

 beginning of development of the supplementary discs. 



noticeable. However, the inception of these formations takes place in 

 such a way that all their elements are formed at the same time and then 

 gradually grow and thicken. During this stage the digestive system 



183 



