Remarks on Myctophum glaciale (Reinh.). å 
first appear at a length of 41 mm. (females) and the dorsal plate 
at a length of 43 mm. (males), in other words when the indi- 
viduals have reached the group II. I have found that the luminous 
plates may be present in specimens belonging to group I, but 
the plates never have the size, in length and especially in breadth, 
as in the specimens of group II, having on the whole the appea- 
rance of being organs in development, a “luminous” stripe rather 
than a well-defined organ. 
Specimens larger than abt. 60 mm. seem to be very rare in 
the Atlantic, as far as I know only captured once, namely, the 
individual of 68 mm. caught by the “Michael Sars” and recorded 
here in the graph., fig. 2°). It is in this connection worthy of 
note that while the specimens belonging to the group I of the 
“Michael Sars” material originate from various stations, the group II 
chiefly consists of specimens captured in a single appliance on 
stat. 80, July 11th; the specimens examined into had spent ovaries. 
Large specimens occur likewise rarely in the Irish collections. 
Holt & Byrne (1911 p. 17) are inclined to ascribe this fact to 
inefficiency of the appliances in capturing swifter fishes. The 
“Helga”, however, employed also a midwater ottertrawl, a gear 
of high fishing capability. 
From the foregoing data I think it justifiable to draw the 
following conclusions:—In the Atlantic M. glaciale spawns 
only once in life, namely when having reached an 
age of 2 years (group I). Most of the individuals 
die sooner or later after spawning or at least be- 
fore getting 3 years old*).—I find these assumptions cor- 
roborated by a remarkable parallel, exhibited by the species in the 
Mediterranean, or more exactly by the smaller race living there. 
Taning (1918) who has had an ample material at hand from 
summer and winter, comes to the conclusion that the Mediter- 
1) No data with regard to size have been published of the rich collections 
of American expeditions. Of the large specimens from the coast of Green- 
land see later on p. 31. 
”) One might object to this:—A group III might have spawned in the 
spring (together with the group II) and died after spawning.—This can not 
be disproved by the collections of the *M. Sars” and the “Arm. Hansen” 
from late spring and summer. The collections of the “Helga” are, however, 
from the year round and do not contain specimens referable to a group III. 
