35 



of the genital apertures — as in 3Ii/sidion — has its own list, which in this animal forms 

 a ring (fig. 31); in the front part of this ring we see a rather large hole (k) which serves 

 as opening to a gland (comp. Mysid. abijssormn). The genital aperture (g) lies up to the 

 part of the ring which is turned towards the median plane of the animal. Contrary to 

 3l!/si(UoH, the distance between the rings varies between being a little greater and very 

 much smaller than the diameter of each. A long way in fmnt of the genital apertures 

 we see two knots a little apart from each other (fig. 3g, r', fig. 3e, o) which show as it 

 were irregular cracks in the thick diitine; no doubt they form the entrances to the recep- 

 taculum seminis (fig. 3e, r) which is odd, much broader than it is long, and at each side 

 bends backward, thus continuing as two almost parallel ducts, which are wide, at the 

 middle sowewhat narrowed, and run to the genital apertures. No spermatophores have 

 been found. 



b. The Male. 



Out of my forty-three species I know the males of thirty-two, viz. of all species of 

 the genera Stenothocheres, Homoeoscelis, Mysidion and Aspidoecia, as well as of twenty-five 

 out of the thirty-foiu- species of Spheeronella. So in nine species of Sphceronella and in the 

 two species of Choniostoma the males are still unknown. AVith respect to the latter genus 

 particularly the gap is keenly felt. 



The male is always much smaller than the adult female — as a rule quite dispro- 

 portionally so. In tlu-ee species only : Splicer, frontalis, S. decorata and (S'. curtipes, its length 

 exceeds ^/a mm. The largest male I know belongs to S. curtipes and measures '92 mm. in 

 length and ^/s of tliis size in breadth. In most species the length is about Vi — Vs mm., and 

 the length somewhat , exceeds the breadth. The smallest normal males I have found in 

 Aspidoecia Normani, two specimens of which were respectively ■147 and -I'SS mm. long. 

 In Mysidion abyssonim the normal male seems to be about •164 mm. long, though I have 

 found two perfectly dwarfish specimens, of which one \\'as 099 mm. long — and this is one 

 of the smallest of adult Copepods hitherto discovered, Imwever, it may be that these two 

 specimens were recently hatched and had not grown to their full size (s. below under »post- 

 larval development «). The genus Homoeoscelis shows least difference between the male and 

 the female, especially H. mediterranea , of which the largest female was -31 mm. long, 

 •32mm. broad and rather flat, whereas the male was ■174 mm. long, -096 mm. broad and 

 equally tliick. The greatest difference between the sexes I have found in Sphcer. microcephala, 

 in ^^•hich the largest female was 1 '44 mm. long , of the same breadth and almost perfectly 

 globular, whereas the male without counting the rostrum was •18 mm. long, 15 mm. broad 

 and ab. -11 mm. thick, wliich gives a volume of between 800 — 1000 times smaller than 

 the female. 



The body, as a rule, is somewhat longer than brcKid, and seen from below, varying 

 from sub -globular to an elongate oval, seen sideways, the back is strongly vaulted, the 



5* 



