756 SUMMARY OF CURRENT RESEARCHES RELATING TO 



North American Ergasilidae.* — C.B.Wilson gives an account of the 

 Bfcructure of Ergasilus, BomolocJius,iTtetuacanthu8,z,n^. other members of 

 this family of parasitic Copepods. He makes a very important contribu- 

 tion to the morphology and embryology of the family, and establishes 

 three new genera. As regards systematic position, the author suggests 

 thai the Iachomolgidas must be kept separate from the Ergasilidaa ; 

 that the Ergasilidse are closely related to the Corycaeidge and Licho- 

 molgidse on the one side, and to the Chondracanthidaa on the other, the 

 four families forming a series ; that the Ergasilinae, Bomolochime, and 

 Tseniacanthinae form a natural series of sub-families. 



Development of Achtheres.f — C. B. Wilson gives a detailed account 

 of the development of Achtheres ambloplitis Kellicott, the American re- 

 presentative of the European A. percarum. The American species is 

 very common on the gill-arches of the rock-bass or red-eye, Ambloplitis 

 rupestris. It is taken as a type of the Lernaeopodidas. 



Long filaments of ovarian cells loosen themselves from the epithelium 

 of the ovary, and pass down into the uterine processes of the oviduct, 

 where the terminal cells of each filament develop into oocytes one after 

 another. The yolk-globules of the egg are evenly distributed through 

 a cytoplasmic matrix. The eggs are fertilized at the mouth of the 

 sperm receptacle as they pass out of the oviduct. There is a migration 

 of nuclei and cytoplasm to the periphery to form blastoderm cells, and 

 these also segment at the surface. The portion of the blastoderm which 

 is to form the ventral surface of the embryo thickens and shows a series 

 of lobes, the future appendages. 



The author describes the nauplius and metanauplius stages which are 

 passed inside the egg, the larva hatching in the first copepodid stage. 

 It is interesting to notice that the nauplius eye is so rudimentary that 

 it is seen only in serial sections. It has neither pigment nor lens. But 

 the most interesting nauplius structure is the attachment filament, begun 

 in the nauplius and completed in the metanauplius stage. It is secreted 

 by a large frontal gland which occupies the whole of the anterior dorsal 

 portion of the cephalon. It is a long, coiled, hollow filament ; the distal 

 end is like a mushroom and attached to the host ; the proximal end is 

 peg-shaped and attached to the gland. The larva emerges in the first 

 copepodid stage (24 to 48 hours) and fastens itself to its host. The 

 filament is transferred from the frontal margin to the claws at the tips 

 of the second maxillaa. In the male the claws are withdrawn from attach- 

 ment to the filament at the time of sexual union, after which the male 

 clings to the female. Sex-distinction appears in the second copepodid 

 stage, which shows all the adult organs. 



The author has made a fine study of this markedly concentrated de- 

 velopment. The nauplius and metanauplius stages are within the egg 

 and fused ; the only free-swimming stage lasts 24 to 48 hours, just long 

 enough to find a host ; the second copepodid stage moults directly into 

 the adult form. 



* Proc. U.S. Nat. Mus., xxxix. (1911) pp. 263-400 (20 pis. and 41 figs.), 

 t Proc. U.S. Nat. Mus., xxxix. (1911) pp. 189-226 (8 pis.). 



