ELLOBIOPSIDAE ' 289 



parasite inside the ovary (referred to in the present paper as ' protoplasmatic excrescences ' or ' root 

 system'). Einarsson describes the chief particulars of the internal part of the parasite: 'The stalk of 

 the parasite, which penetrates the carapace, may be followed in the sections, often dividing into 

 branches which run horizontally through the internal organs, but sometimes it is confined to one 

 strong continuation of the stalk' (loc. cit., p. 158). In the infested specimens of Thysanoessa Einarsson 

 found that the external sexual characters are totally absent; it therefore seemed probable that the 

 parasite castrates its host. Examination of sections of the ovary of a mature female and of an infested 

 specimen showed that in the latter the ovary was completely disorganized. 



Recently I published a short paper on the organs of absorption in a species oi Amallocystis (Boschma, 

 1948), a preliminary communication dealing with a part of the material from the Discovery collections. 

 The parasites of the Euphausiids were mentioned here as A.fagei; provisionally the peculiar manner of 

 attachment to the region of the genital gland of the host was considered as a sufficient indication of its 

 specific distinction. In this paper I mentioned protoplasmatic excrescences penetrating from the organ 

 of fixation into the ovary (at the time I did not know that Einarsson already had described these 

 prolongations of the organ of fixation), and showed that the cuticle of the organ of fixation possesses 

 a distinct sieve plate through which the protoplasmatic excrescences protrude. Page (1936) already 

 had given as his opinion that the organ of fixation of Amallocystis not only serves as a means of attach- 

 ment of the parasite, but that it also functions as an organ of absorption of food. After having found 

 the sieve plate and the protoplasmatic excrescences emerging through this plate into the ovary I con- 

 cluded that these are the real organs for the absorption of food ; the cuticle of the organ of fixation 

 itself is too thick to allow the passage of food. 



A more detailed description of the Discovery material follows here. 



The parasites are found slightly behind the middle of the dorsal surface of the carapace of the host. 

 Their external part consists of a bundle of cylindrical bodies which are divided into a series of elements 

 by distinct transverse grooves. On the larger specimens of the Euphausiids the parasites may show 

 a considerable number of these cylindrical bodies; in one specimen on Etiphausia vallentini 

 (PI. XXXVIII, figs. I, 4) fifty of them could be counted. As a rule, however, this number in the parasites 

 on E. vallentini does not exceed thirty (as in the specimen in PI. XXXVIII, figs. 2, 5). The parasites 

 of E.frigida have approximately the same number of cylindrical bodies (PI. XXXVIII, fig. 8). On the 

 parasites of E. recurva (PI. XXXVIII, fig. 6), E. Iticens, E. hemigibba (PI. XXXVIII, fig. 9), and 

 Thysanoessa gregaria (PL XXXVIII, fig. 7) ten to fifteen of these cylindrical bodies were counted. 



The cylindrical bodies vary in length from 0-5 to 2-5 mm., and their transverse diameter is from 

 0-13 to 0-33 mm. They consist of up to eight elements, the proximal of which, the trophomere, is more or 

 less conical, whilst the others, the gonomeres, have a more or less globular shape. The distal gonomere 

 may grow out into a more elongated body (some of these are visible in PI. XXXVIII, figs, i, 4), which 

 may easily break off from the top. The following gonomere then may show a distinct scar (visible in 

 some of the gonomeres of PI. XXXVIII, figs. 2, 10). Probably, however, this is not the natural manner 

 of detachment of the ripe gonomeres. Numerous distal gonomeres show at their free extremities 

 a kind of filament (distinctly visible in PI. XXXVIII, figs. 8,11), which consists of the shrivelled cuticle 

 of the preceding gonomere from which apparently the spores have been set free. 



As a rule the parasites of large specimens of the host are pronouncedly larger than those infesting 

 smaller specimens of the host. Measurements of the transverse diameter of the gonomeres of various 

 specimens yielded the following results. Two specimens on Etiphausia vallentini, gonomeres 0-28- 

 0-33 mm.; one specimen on E. frigida, gonomeres 0-28-0-33 mm.; another specimen on E. frigida, 

 gonomeres o- 16-0-23 mm-; specimens on E. hemigibba and on E. recurva, gonomeres o- 13-0- 16 mm.; 

 specimen on Thysanoessa gregaria, gonomeres o- 13-0- 16 mm. 



