already has its final circular shape, but the sex system has not yet been 

 completely developed. The approximate sizes of the worms during that 

 stage are: length 0. 11 - 0. 13 mm, width 0. 04 - 0. 07 mm; length of the 

 disc 0. 05 - 0. 06 mm with a width of 0. 08 - 0. 09 mm; the pharynx is 

 about 0. 025 x 0. 020 mm; the lengtli 'of the first pair of middle hooks is 

 0. 043 - 0. 046 mm and of the second pair 0. 038 - 0. 040 mm; that of the 

 middle connecting plate about 0. 045 mm; and of the lateral plates 0. 045 - 

 0. 047 mm; the sizes of the supplementary discs (at rest) 0. 03 x 0. 035 mm. 



The further development takes place nnainly by way of the for- 

 mation of the sex system and the strengthening of the structures of the 

 attaching apparatus which serve for the articulation of the middle plates 

 with each other and the middle hooks. Considerable growth of the worms, 

 which increase almost three.^_tj,me s in length in comparison with the stages 

 just described and whixjh already have a fully developed attaching apparatus, 

 takes place during this time. .One must also note that the inception of the 

 copulatory organ takes place almost directly after the formation of the 

 attaching plates and the sex systenn begins to function and the worms 

 deposit eggs much before reaching their final sizes. 



11. The development of Calceostomella Palombi P- 171 



In contrast to all preceding genera, Calceostomella 

 is characterized by the fact that during the attachment of the adult indi- 

 vidual the basic significance is acquired by the attaching disc itself and 

 not its armature which is developed so weakly that until the present 

 time it was not even really known whether the edge hooks exist, or if they 

 exist what is their number. As our studies of C^ inerme Parona and 

 Perugia have shown, the attaching armature of this species corresponds 

 to that of Dactylogyridae and consists of 12 typical edge hooks and two 

 middle hooks. The adult _C. inermis (Fig. 189) differ by a strongly 

 developed glandular fringe of the anterior end of the body, by relatively 

 large testes and strong development of vitellaria which almost fill the 

 entire body of the animal. The copulatory organ is chitinous, with 

 powerfully developed prostatic glands. The development of representatives 

 of the genus has not been studied. We obtained a free-swimming larva of 

 C. inermis at the Sebastopol Biological Station (on the fifth day after the 

 deposition of eggs); during July, 1935 the worms which were collected 

 from the Gorbil (Corvina nigra Salv. ) (Humpback Salnnon, nobis) in- 

 tensively deposited eggs. The larva which emerged from the egg is cigar- 

 shaped and has a length of about 0. 1 mm and a width of 0. 03 mm. The 

 ciliary epitheliunn is well-developed and of the usual disposition. The 

 eyes number 2 pairs and are relatively large and are located in front of 

 the pharynx. The attaching disc is already sharply separated from the 

 rest of the body in the larvae which emerges from the egg. The interior 

 organization of the larva is the same as in Dactylogyrus . The attaching 



184 



