83 



species have the distinct negative character of wanting trunk-legs and caudal stylets in both 

 sexes, for as there are species which, though wanting these organs in one sex, not in the 

 other, or through the male having trunk-legs, but no caudal stylets, form a transition to the 

 species in which both sexes possess trunk-legs and caudal stylets, one cannot very well set 

 apart the first mentioned species as a separate genus. If I can find no leading principle 

 to guide me in carrying out the division of a large genus, tJie elements of which seem to be 

 heterogeneous, and if I am not obliged to undertake a division in order to bring aboid an 

 equivalence with previously established acceptable genera, I prefer putting off the division till 

 the discovery of neiv forms has thrown new light on the question. If I had had to subdivide 

 Sphceronella, the result would have been, not two or three, but six or seven genera (some of 

 which would have consisted of only one or a couple of species), in order to establish a pretty 

 correct equivalence, but these new genera would not have been tolerably equivalent with 

 such types as Homoeoscelis, Mysidion etc. 



c. Characters of the Family. 



An examination of the genera will show very clearly that, in spite of several diffe- 

 rences, they are all very closely related and belong to the same family. We will here 

 attempt to give a summary of all its more important characters, some of which separate it 

 from one, some from another, of the rather numerous families of parasitic Copepoda, for it 

 would be impossible to give a condensed characteristique with merely exclusive features, our 

 knowledge of several points in the organisation and development of other families being 

 too defective. 



The adult Females are ovate or sub-globular. The head occupies only a smaller or a 

 minute part of the greatly swollen, unsegmented body; the abdomen is comparatively rather small 

 and unsegmented, or mostly altogether wanting. Antennulse 1-3-jointed; antennae small or wan- 

 ting; rostrum good-sized, comparatively stout with cup- or funnel-shaped mouth provided with a 

 border formed by a membrane which is interrupted only in front and supported outside by free 

 hairs ; maxillulse consisting of a basal part almost entirely fused with the rostrum, and of two 

 or three usually setiform branches ; maxilla? short and powerful prehensile limbs consisting of a 

 stout basal joint and a slender, 1- or 2-jointed, somewhat claw-shaped, distal part; maxillipeds 

 rarely wanting, mostly appearing as good-sized grasping appendages, consisting of a long, rather 

 stout basal joint and a shorter, slender, 2- or 3-jointed distal part. We often find two pairs of 

 rather small or minute trunk-legs, each of which consists of one single joint or sometimes of a 

 peduncle with one or two unjointed branches; the legs are wanting in not a few species. Caudal 

 stylets present or wanting. Some species, at least, can hinge themselves by an adhesive plate 

 or a frontal thread. Spermatophores (found in many species) consisting of a globular or oval 

 vesicle on a rather long thread-shaped stalk. 



11* 



