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All these facts strongly support the correctness of the above-quoted hypothesis
put-forward by G. W. MÜLLER in 1898 as to the reproductive oecology of this species.*
According to this hypothesis the specimens of the first to the fourth columns of the above
table probably are to be interpreted in the following way:
1) The females of the fourth column represent specimens whieh have either not yet
had their planktonic period, in other words have not yet been fertilized or else have just
finished it.
2) The females in the third column are somewhat older; tliey have just definitely
returned to a life of creeping and digging in the mud of the bottom owing to the breaking
o ff of their natatory bristles on the second antennae.
3) The females in the second column are still older; eggs had been pressed out into
their brood chambers for further development there.
4) The females in the first column are the oldest; their brood chambers had just been
emptied.
The faet that the eggs in the ovaries of the females of the third column were often very
small indicates that the natatory bristles are probably broken off fairly soon after fertilization.
With regard to the breaking off of the natatory bristles on the exopodite of the second
antenna it is, as G. W. MÜLLER has pointed out, quite impossible that this is a case of accidentai
mutilation. This is supported, not only by the reasons given by this author, but also by the
faet that the points of the bristles on the second to the fifth exopodite joint on this antenna are
practically never broken, although tliey are very line and although these bristles are often
somewhat longer than the broken natatory bristles on the following joints. — With regard
to the way in which the long natatory bristles are broken off nothing can be decided with
certainty. It does not seem improbable to me, however, that G. W. MÜller’s assumption
that they are bitten off is correct. An investigation of these bristles on the fe males of the fourth
category gave a negative result; no structural alteration could be observed in the region where
the breaking off takes place.
What happens to a female after her brood chamber has been emptied?
It is perhaps too soon to give an opinion on this question. But it seems to me not
improbable that they die rather soon afterwards. This is indicated by the faet that no moults
seem to occur in the species of this genus after sexual maturity is attained. (Our knowledge
in this respect is, however, very limited; cf. G. W. MÜLLER, 1894, p. 188.) Without any moult
followed by a regeneration of the natatory bristles of the second antenna, it is, of course,
impossible for these females to accompany the males when they soar aloft in the plankton. The
possibility of fertilization during a continued life in the mud of the bottom is, of course, not
exeluded, but does not seem very probable. Nor is it impossible that a sufficient quantity of
sperm remains in the receptacula seminis for the fertilization of a new hatch of eggs. Nor,
of course, is the possibility of a parthenogenetic development of the eggs in the ovaries fully
* At about the same time as G. W. Müller a Swedish scientist Professor .1. G. Andersson, who investigated the
Ostracod material of the Swedish State M u s c u m, put forward quite the same hypothesis; the results of his
investigations, which are still in manuscript, were, however, never published, I too arrived at the same result quite
inde-pendently of these two investigators.
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