47 



viz. Sphfpr. Munnopsidis and the two species of Choniostoma, lay tlie largest number of 

 eggs. In a specimen of Ch. mirahile with eleven ovisacs I counted the eggs in one of these 

 presumably of middle size, and I found 1057 eggs, so the number of eggs laid by this 

 specimen may be said to amount to 11,620, and if we take this figure as the noimal 

 quantity in Ch. mirobiJc of the Kara Sea, at any rate we do not exaggerate. In Spluer. 

 Munnopsidis the number of eggs seems to be even much higher, however, it would scarcely 

 be possible to calculate the exact amount. Between these last-mentioned species and 

 Stenofhocheres egregius the other species present a variety of transitions, as far as fertility 

 is concerned. In a following chapter about distribution etc. I shall have an opportunity 

 of making some further observations on these rather i-emarkable differences. 



II. The development of the eggs. As for the division of the germ and the earlier 

 part of the embryological development, which I have not studied myself, I shall refer to the 

 representation of Salensky. As in all Copepoda a Naupliu.^ stage is developed (pi. XI, fig. 1 c 

 and fig. Id); but this stage never becomes free, it evolves itself into the stage of a highly 

 organised larva, of which a detailed description is given below. When this larva, which 

 coi'responds with the first Cyclops stage in other parasitic Copepoda, is fidl-grown, it breaks 

 out of the egg-membrane and of the ovisac. As for the details concerning the development 

 of the Nanplius stage and of the larva, I must again refer to Salensky. 



It may be added that in material preserved in spirit (and I have seen no other) 

 the ovisacs, when younger, are of a light yellowish coloiu', but they gradually get whiter, 

 as the larva; are developed. 



d. The free Larva. 



I. The Material. Of several species 1 iiave found free larvae, wliich were either 

 swimning out of, or had recently swum into the marsupium, and these specimens, of course, 

 were excellent, showing the normal shape of the larvae. Of a number of species I have 

 procured a rich material of larva by pulling them out of an ovisac; they were good enough 

 when taken while about to break out of the egg- membrane, though the body might be 

 somewhat soft and not extended in its full length, thus showing a vaguer outline which did 

 not quite correspond with that of the swimming specimens. Sometimes I had to content 

 myself with younger animals, which had to be pulled out of their egg-membranes, and which 

 had indeed a well-developed mouth, maxillae, maxillipeds etc., but whose cephalothorax was 

 decidedly shorter and stouter than those of the full-gro-mi larvae, and which also showed 

 other signs of unfinished development, so that no reliable observations could be made of 

 difficult parts, as e. g. the branches of the maxillulae. Finally, of a few species I had only 

 larvae which had swum into the marsupium of a new host, where they had attached them- 

 selves (.1: below), and in these the cephalothorax, as a rule, was shorter and broader 

 than in the free specimens. Of some species I had larv* of tliis kind as well as of others, 



