4. THE LARVAE
109
layer of circular muscle. The fully formed spermatophore is stored in
the ejaculatory duct for some time and a second spermatophore is
usually present in the spermatophore sac of the vas deferens during the
breeding season.
a
- -
i
\ ega
FIG. 40. Diagram of the male reproductive system of Meganyctiphanes norwegica. The
left-hand side shows the regions a-b, b-c, c-d, d-e, and e-f where the various
components of the spermatophore are formed. ega, external genital aperture ;
ej, ejaculatory duct ; lp, lateral pocket ; sps, spermatophore m c ; t, testicular
vesicles ; vd, was deferens.
Ruud (1936) states that only one spermatophore, usually the left,
develops in Euphausia krohnii and Baker (personal communication)
finds that only the left one develops in other species of Group A of the
genus Euphausia-E. americana, E . eximia, E . krohnii, E . mutica,
E. brevis, E . diornedeae, and E . recurva. Baker finds that this does not
always apply to E . recurva because he discovered one specimen in which