Il8 NATHAN FASTEN. 



a small, spiral gland can be distinguished (Figs. I and 9, c. g.), 

 which, under the microscope shows strong powers of refracting 

 light. These structures later develop into the cement glands of 

 the adult (Figs. 10-11, e.g.). 



FERTILIZATION. 



About two and a half or three weeks after the attachment of 

 Lernceopoda edwardsii to the brook-trout, the copeopod is ready 

 to copulate. In two earlier papers (Fasten, 1912 and 1913), the 

 attachment of the parasite to the host was discussed. As already 

 stated, the mature male is very much smaller than the female. 

 In order to fertilize the female, the male must release his hold 

 on the gill of the brook-trout, and attach himself to the lower 

 extremity of the female's body, in the neighborhood of the genital 

 pores. This is accomplished in the following manner. When 

 mature, the male, though. still attached, makes circling move- 

 ments with his body, thus coming in contact with a female. As 

 soon as this occurs, the male clasps her with his maxillipeds, and 

 at the same time, withdraws his second maxilla? from the filament 

 of attachment to the gill. Then he moves towards the female's 

 genital pores, and places himself in position for fertilization. 

 'The position assumed is shown in Fig. I. These observations 

 are similar to those made by Wilson (1911), on the copepod 

 .Achtheres ambloplitis Kellicott, infecting the rock bass. 



When once in position, the male brings forward the posterior 

 region of his body to a position near the genital pores. The 

 spermatophores are then ejected through the ejaculatory pores, 

 and by the aid of his free maxillae the male attaches them near 

 the genital openings of the female (see Fig. 8). The cement 

 found in the spermatophores is the substance that makes them 

 adhere tightly. As soon as they are attached, the spermatozoa 

 wander through the genital pores and are conducted into the 

 spermatheca, where they are stored until the eggs are mature for 

 fertilization. When the spermatozoa have all migrated into the 

 spermatheca, the spermatophores collapse, and become trans- 

 parent, shell-like, yellowish spheres (Figs. 9-10, sp.}. 



The female may be fertilized more than once. As many as 

 six spermatophores were found clinging to the genital pores of 



