154 
BULLETIN OF THE BUREAU OF FISHERIES 
Breeding habits . — The spawning of Meganyctiphanes has not actually been 
observed either in American or European waters, but it seems certain that this 
genus either does not carry its eggs with it at all after they are extruded, as some 
other euphausiids do, or that it nurses them only for a brief period at most, both 
because ovigerous females have never been seen, so far as 1 can learn 82 (Holt and 
Tattersall, 1905), and because eggs probably ascribable to this species have been 
found free floating in the one-celled stage by Sars (1898) and by Lebour (1924a). 
It is true that the eggs of Meganyctiphanes have not been identified with 
absolute certainty from among the plankton. Sars (1898), however, thought it 
probable that at least some of the euphausiid eggs 83 about 0.7 to 0.8 millimeter in 
diameter, which he found in Christiania Fjord where Meganyctiphanes is plentiful, 
had that parentage. Similar eggs had already been recorded from the Clyde area, 
a center of abundance for Meganyctiphanes, by Brook and Hoyle (1888). Holt 
and Tattersall (1905, p. 103), too, have assigned to this genus certain loose ova 
found side by side with Meganyctiphanes and occasionally even clasped between 
its thoracic legs, among various articles of prey, though without describing the 
dimensions or appearance of the eggs in question. Lebour (1924) has recently 
ascribed to this same parentage certain euphausiid eggs from the English Channel, 
because of the characters of the larvse hatching therefrom. 
Brook and Hoyle, Sars, and Lebour all agree in describing these eggs (the 
correct identification of which is made practically certain by cumulative evidence) 
as inclosed by a perfectly transparent capsule 0.7 to 0.8 millimeter in diameter, the 
ovum proper having a diameter of approximately 0.3 to 0.4 millimeter. Thus, when 
first set free in the water they much resemble buoyant fish eggs with wide 
perivitelline membrane; but cleavage being holoblastic and the development of the 
nauplius plainly visible within the egg, thanks to its transparency, their crustacean 
nature is apparent almost from the beginning. Euphausiid eggs are so characteristic 
in appearance, also, that there is no danger of confusing them with any other buoyant 
eggs- 
Our own hauls in the Gulf of Maine have yielded considerable numbers of eggs 
of this same type and size in various stages of development. We first detected them 
in a surface tow in the Grand Manan Channel, off Campobello Island, August 19, 
1912 (in the report for that year (Bigelow, 1914, p. 104) they were referred to through 
eri’or as “balanus” eggs). These were for the most part in early cleavage stages, 
a few in various stages up to the fully formed nauplius ready to hatch. Eggs of this 
same type, as well as the recently hatched nauplii, were again taken on the 22d of 
the month off Penobscot Bay (station 10039). Since that time we have detected 
similar eggs in the Fundy Deep and off Mount Desert Island in June (stations 10282, 
10284, and 10286, June 10 to 14, 1915) and off the mouth of the Grand Manan 
Channel on July 15, 1915 (station 10301). It is not safe to say that all these eggs 
are Meganyctiphanes, for Lebour (1924) found eggs of Thysanoessa inermis indis- 
tinguishable from them; but the strong probability that at least part of them belong 
82 The considerable series of large adults which I have examined contained none. 
83 Metschinkoff (1871, pi. 34, fig. 1) first described the peculiar and very characteristic buoyant eggs of this group of 
pelagic Crustacea. 
