ELLOBIOPSIDAE 



301 



B. THE SPECIMEN ON HOPLOPHORUS NOVAE-ZEELANDIAE DE MAN 

 The specimen is attached to the ventral surface of the abdomen of its host, and the external part 

 protrudes through the integument joining the first and second abdominal segments. The parasite was 

 examined externally only, but the pleurae of the left first and second abdominal segments were removed 

 to obtain a better view of the parasite. In the side view of the external parts of the parasite (Fig. lib) 

 the pleurae are represented to show the situation of the parasite in regard to its host. In the figure 

 approximately 100 trophomeres with their gonomeres are visible. If we assume that about one- 

 fifth of the whole number of trophomeres is visible here, the total number amounts to 500, a 

 considerably smaller number than that of the type specimen. As in the latter the trophomeres are 

 united in tufts that with usually long stalks originate from a common centre. The whole external mass 

 in side view has a larger diameter of about 5 mm., and a height of about 2 mm. 



Fig. II. Amallocystis umhellatus n.sp., specimen on Hoplophorus novae-zeelandiae De Man. a, tuft of stalks with trophomeres 

 and gonomeres; b, external part of parasite in situ on host, c, carapace; I, first abdominal segment; II, second abdominal 

 segment; III, third abdominal segment, x 15. 



Fig. 11 a represents a single tuft of trophomeres and gonomeres. As a rule each trophomere bears 

 three gonomeres, which are of a globular shape except the distal gonomere which is usually slightly 

 more elongated. The diameter of the gonomeres varies from 140 to 195//. They are, therefore, slightly 

 smaller than those of the specimen on Hoplophorus grimaldii, but in all other respects the external part 

 of the two parasites is quite similar. 



The host of the type oi Amallocystis umbellatus, a specimen oi Hoplophorus grimaldii Coutihre, appears 

 to be a female. The pleopods of the first and second abdominal segments seem to be of normal shape. 

 Every trace of an appendix masculina as it occurs on the second pleopod of the male is absent. More- 

 over, the anterior angle of the first abdominal pleuron is evenly rounded, without any indication of an 

 incision, so that this pleuron has the typical character of the female.^ 



The host of the other specimen of Amallocystis umbellatus, Hoplophorus novae-zeelandiae De Man, 

 again has all the characters indicating the female sex. Here also the pleopods of the first and second 

 abdominal segments show a normal development, whilst the appendix masculina is entirely absent. 

 As in the former specimen there seem to be no indications of a deviation from the normal type as 

 a result of the parasitization. 



1 Cf. Chace, Jr., F. A., 1940, Plankton of the Bermuda Oceanographic Expeditions. IX. The Bathypelagic Crustacea. 

 Zoologica, vol. xxv, p. 188 (concerning Hoplophorus grimaldii Coutiere) : ' Although there is a well developed appendix masculina 

 in the adult males of this species, there is also a sexual distinction involving the first abdominal pleuron as in the preceding 

 species ; in the male, the lower anterior angle of this pleuron is deeply incised so that the angle formed approaches a right angle, 

 while in the female this angle, if present at all, is very obtuse.' 



