302 



DISCOVERY REPORTS 



Amallocystis capillosus Fage 

 Amallocystis capillosus Fage, 1938, p. 287. 



Material : 



St. WS 748 (53° 41' 30" S, 70° 55' 00" W), 16. ix. 1931, net NR, depth of net 300 (o- ?) m., 2 ex. on Pasiphaea 

 acutifrons Bate (PI. XLI, figs. 3, 4). One specimen, transverse sections of part of host containing parasite, Delafield's 

 haematoxylin (Figs. 12-16). 



The parasite is attached to the basal part of the rostrum of the host, where it forms a pronounced 

 ridge on the carapace. The external part of one of the parasites is a mass of stalks with trophomeres and 

 gonomeres with a larger diameter of about 4-6 mm. and a height of about 3-5 mm. (PI. XLI, fig. 3) ; the 

 corresponding dimensions of the external part of the other parasite (the sectioned specimen) are about 

 4 by 3-5 mm. (PI. XLI, fig. 4). In the external masses of each of the two parasites about fifty to seventy 

 trophomeres can be counted, though originally there must have been a considerably larger number, as 

 in Fig. 15 already parts of eighty-three trophomeres are visible, the majority of these being sections of 

 the stalks. Apparently a great number of trophomeres have become detached from their stalks after 

 preservation of the parasites. 



At each side of the carina which forms the proximal part of the rostrum of the host there is a bundle 

 of slender stalks of various lengths, sometimes extending rather far in an anterior direction. At its 

 extremity each stalk passes into a trophomere of an elongate shape, more or less cylindrical with 

 a tapering proximal part. On the top of each trophomere there may occur one gonomere of elongatedly 

 oval shape, which may have a length of about o-6 mm., whilst the trophomere may be about twice as 

 long. The transverse diameter of the trophomeres and the gonomeres is from 0-15 to 0-25 mm. 



The internal part of the parasite was studied in transverse sections of the rostral region of the host. 

 Drawings of three sections containing the internal part of the parasite are given here. The most anterior 

 (Fig. 12) is at a distance of 60 // from the following (Fig. 13), the latter at a distance of 170// from the 

 next figured section (Fig. 14). Moreover, part of a section not containing internal parts of the parasite 

 is drawn in Fig. 15. This section is at a distance of 330// from the one drawn in Fig. 12. 



The series of sections begins at the posterior region of the part of the host sectioned, so that the 

 right side of the host is found at the left side of the figures. 



In Fig. 12 at each side of the carina (the proximal part of the rostrum) there is a number of stalks, 

 of trophomeres and gonomeres. Some of the stalks are drawn with a double line, as they have a rather 

 thick cuticle ; they belong to the proximal portions of the external part of the'parasite. At the right side 

 of the basal part of the carina (left in the figure) the latter is pierced by a hole through which the 

 external part of the organ of fixation of the parasite protrudes. This external part here forms a short 

 tube which at its top divides into a number of stalks. Between the carina and the antennal gland of the 

 host (indicated by a broken line) there is an irregular mass of cuticular matter belonging to the 

 parasite ; this mass represents the proximal part of the root system. The figure further shows a number 

 of roots extending into the tissues of the host (the roots indicated with a rather heavy line). 



Fig. 13 shows again at each side of the carina a number of stalks, of trophomeres and of gonomeres of 

 the parasite. The organ of fbcation in the region of this section attains its largest size. It is a more or 

 less irregularly globular organ, which in the figured section forms an excrescence penetrating through 

 a hole at the left side of the basal region of the carina (right in the figure). This excrescence is of 

 a similar shape to the one in Fig. 12; at its top it divides into a number of stalks. The organ of fixation 

 itself is covered with a rather thick wall, which in its lower part shows a peculiar structure that must 

 be considered to be homologous with the sieve plate as it occurs in Amallocystis fagei. Under this sieve 

 plate there is a dense mass of cuticular matter with a great number of openings ; it is a complicated 



