ELLOBIOPSIDAE 311 



trophomeres and in the dimensions of the trophomeres and the gonomeres. Gonomeres of small 

 specimens may be less than half as long and broad as those of large specimens. The measurements 

 of specimens on Thysanoessa from Icelandic waters were taken from the figures in Einarsson's paper 

 (1945, fig. 836, c). If these measurements (o-i mm.) are correct the trophomeres and gonomeres of 

 these Icelandic specimens are still smaller than those of the parasites on Thysanoessa from the Antarctic 

 (o- 13-0- 1 6 mm.). For the present it must remain undecided whether the Arctic form really is specifically 

 the same as the Antarctic form. The available data point to a specific unity. 



The specimens of Amallocystis capillosiis dealt with in the present paper correspond in all important 

 characters with the specimens described by Fage. The trophomeres and gonomeres have the same 

 shape and approximately the same dimensions. It is interesting that the specimen described in detail 

 in the present paper pierces one side of the base of the rostrum of its host in two separate places. 

 Undoubtedly normally there is one of these holes only at each side of the rostrum, as in the specimens 

 described by Fage. 



THE GENERA OF THE FAMILY ELLOBIOPSIDAE 

 The data obtained in the examination of the three species of the genus Amallocystis dealt with in the 

 present paper give occasion for a comparison of these results with the data in the literature concerning 

 the other genera of the Ellobiopsidae. The most striking fact presenting itself is the similarity of the 

 genera Ellobiopsis and Amallocystis. With these two the genus Rhizellobiopsis seems to form one group. 

 The comparatively little-known genus Ellobiocystis appears to be rather distinct from the group of 

 three genera mentioned above, and the genus Parallobiopsis differs sufficiently from all the other genera 

 of the family for it to be regarded it as a distinct group by itself. The arguments for this division of the 

 family into different groups may be set forth in more detail. 



In fully developed specimens of Ellobiopsis chattoni the external part may have a length of 700// and 

 a transverse diameter of 350//. Then the pear-shaped external part is divided into a smaller trophomere 

 and a larger gonomere (CauUery, 1910; Jepps, 1937), the gonomere being about twice as long as the 

 trophomere, or having at least twice the volume of the trophomere. The parasite is attached to one of 

 the anterior appendages of its host by a distinct organ of fixation which as a strong rod penetrates into 

 the appendage. Apparently it is not only an organ of fixation but has also the function of absorbing 

 the food. 



The specimen of £". chattoni described and figured by Steuer (1928, ig^^b, 1933), and regarded by 

 him as an adult stage, shows a large pear-shaped trophomere capped by a much smaller globular 

 gonomere, the length of the trophomere being 3 1 1/<, that of the gonomere 1 1 1//. Moreover, in Steuer 's 

 specimen the groove between the gonomere and the trophomere is much more pronounced than in 

 Caullery's specimens. The specimens figured by Apstein (191 1) and by Willey (1920) show a small 

 gonomere separated by a distinct groove from the much larger trophomere; in these respects they 

 correspond with Steuer's specimen. The differences between the two forms possibly point to a specific 

 distinction. For the present this must remain undecided. 



An undoubtedly specifically separate form is E. elongata Steuer (1932 c). When fully developed it 

 consists of a cylindrical trophomere with a length of 250//, and at the top of this trophomere are two 

 globular gonomeres with a diameter of 70-80//. Besides being much smaller than E. chattoni this 

 parasite is distinguished by its peculiar shape. As in E. chattoni the stalk penetrates into the 

 appendage of the host as a long thin organ of fixation. 



The external part of E. chattoni, and even more distinctly that of E. elongata, closely corresponds 

 with one of the external excrescences of the species of the genus Amallocystis. Principally Amallocystis 

 is nothing but a compound Ellobiopsis, in which the organ of fixation has become more complicated 



