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that they must have been laid at different times, as not developed eggs, eggs with
embryos and empty shells are to be found among each other.
The opening of the egg occurs in the manner that the shell splits in the front
part in a fissure which runs down the middle of the dorsal and ventral side to a
little beyond the middle (Pl. I, fig. 7); two lateral valves are thus formed. I have
not been able to observe that the fissure is preformed in the egg-shell.
It is mentioned above that the eggs are attached with, or generally more or less
imbedded in a glue-like substance. In the specimens, which are all preserved in
spirit, that mass is hard. The question then arises how the larvæ come out; the
hard mass must prevent the opening of the egg, and even if the egg was opened, it
would be difficult or impossible for the larvæ to get out, and especially in the cases
where the eggs are lying in many layers above each other, and those at the bottom
thus are quite enveloped; here the eggs lying farther down in the egg-mass certainly
must be destroyed. I suppose therefore, that the glue-like substance mentioned,
in its natural state, when the egg-mass is floating in the sea, is gelatinous, so
that it permits the egg to open itself and the larvæ to get out. There also exists
a communication which confirms this, Witlaczil says (1, c. 233) of the eggs taken on
the expedition of "Vettor Pisani" ". . . die von einer wahrscheinlich ursprünglich
gallertigen Masse umgeben waren. Diese Masse qnoll im Wasser wieder auf —" It
is not said how the eggs had been treated before they were put into water, probably
they had been dried. One of my specimens also shows open egg-shells sitting quite
surrounded by the glue-like mass, which thus certainly must have been soft.
When the larvæ have escaped they probably very soon undergo the first moult;
the specimen No. 18, which unfortunately has been destroyed, was a piece of drift
timber, on which eggs and cast larval skins were sitting. The first moult has then
occurred at the place where the larvæ had been bred, and certainly shortly after the
creeping out. Witlaczil states (l. c.) the same, founding his opinion on the fact found
in other Hemipteres.
As to the mature embryos I can only confirm Witlaczil’s communication, that
they do not quite fill the whole shell, and that the long middle and hind legs bend
down round the end of abdomen, and then along the dorsal side up towards
the head.
According to what has been stated above the following may in general be said:
The eggs of the Halobates are comparatively large, about 1 mm long, elongated
oval or cylindric with rounded ends. The ventral side is arched, the dorsal side flat
or slightly arched; the front end somewhat broader than the posterior end. The
colour varies gradually from yellowish white to red, as the development advances.
Ghorion is solid, thicker or thinner; it is simple, without sculpture, or with a more
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