402 Sidney I. Kornhauser 



III. Material and Methods. 



A. Material. 



The material was gathered at Naples, from April to August inclusive, 

 1913. HersiUa apodifomiis (Phil.) is a small semi-parasitic Copepod, 

 found crawling in the gill Chambers and over the abdomen of Callianassa 

 subterranea (Leach.). It is a flat, "Apus-like" form (Figs. A — B), 

 obtained usually in pairs, the males being attached either to much larger 

 mature females or to immature females^) (Fig. C), which are often smaller 

 than the males themselves. The males hold tightly, their posterior maxil- 

 lary appendages being highly modified into clasping organs which fit per- 

 fectly into lateral recesses in the fourth abdominal segment of the females. 

 The antennae and first swimming legs also aid in clinging fast. Hersüia 

 is evidently a case in which the males are becoming entirely dependent 

 upon the females for locomotion and nutriment. This is supported by 

 the facts that the swimming legs of the male are much less developed 

 than those of the immature female of a size equivalent to that of the 

 male, and that the abdomen of the female is so constructed that the 

 faeces pass directly to the mouth-parts of the attached male. As shown 

 in Figure C, there is a dorsal longitudinal groove in the abdomen of the 

 female, posterior to the termination of the intestine; and over this groove 

 are situated the mouth-parts of the male, when attached. In the adult 

 female, this groove is deeper and more complicated; for here it serves 

 also as the passage way of the spermatozoa into the receptaculum seminis, 

 which lies dorsal to the intestine. It is an interesting fact that the male, 

 when attached to a mature female, always possesses the same coloring 

 pigment (yellow, orange, or red). This pigment Variation is probably 

 dependent upon the food. A microscopical comparison ob the material 

 found in the digestive tracts of paired individuals showed that the food 

 of the male was always in a much finer State of mastication than that 

 of the female. 



B. Methods. 



Although Hersüia is by no means abundant, in five months I was 

 able to get about six thousand pairs. They were dislodged from their 

 hosts by squirting them with a strong pipette into a dish of sea water. 

 Before fixing, it was found best to rinse them quickly in distilled water ; 



1) Immatiire females of foiu- stages were found with attached males. The siiccimen 

 shown in Fig. C is from the second of the four stages found on Callianassa, there being 

 still two stages to bc passed through before the adiüt form is reached. 



