34 Alf Wollebæk. | [No. 12 
than those of Sclerocramgon. In both cases the larvae remain for 
a time beneath the body of the mother, and both have certain limbs 
specially adapted to this existence: but there is the interesting 
difference that while the larvae of Scleroeramgon have generally the 
last 2—83 posterior pereiopods developed into clinging organs, it is 
the chelipeds of the larvae of Astacus which perform this funetion. 
Both undergo å change from å post-embryonic stage where they 
-remain elinging to the mother, to an existence at the bottom in whieh 
they have attained all the essential characteristics of the full-erown 
animal. 'The physiological resemblance between Scleroeramgon feros 
and Astacus fluviatilis during the course of their development is the 
more interesting when we consider the relatively great systematic 
distance betwen these two species and their very different bathy- 
metric distribution: the first a salt-water species existing at great 
depths, the latter a fresh-water species frequenting the shores of 
lakes and rivers. 
»  Breeding season. During the Northern Sea expedition of 
1900 s/s "Michael Sars” likewise secured many fully-developed 
specimens of Se. ferox in the locality previously-mentioned east of. 
Iceland. Not only were larvae found smaller than 11 mm. elinging 
to the mother, but specimens were also obtained of the following 
S1Zes :— 
1. Unberried Feémales: 382—35—40—60—65—65—7598 
—110—110—110—115 mm. Of these one specimen about 
110 mm. long had just cast her spawn. 
Berried Females:  110—115—115—120—1201920mm 
3. Males: 8385—35—38—47—70—"70—=76—85 5555 
90—95—95 mm. [These have been measured in every in- 
stance from the margin of the telson to the tip of the 
rostrum|. 
R) 
Judging from the material in our possession I should say sum- 
mer is the period when the larvae of this species are hatehed. The 
greater part of the females were berried on the 28th July, and the 
same was the case with specimens secured near Jan Mayen on the 8th 
August (100 —120 meters). In å few cases larvae were found al- 
ready hatched, while in others the eggs were less developed, and 
in others again it was quite evident that the spawn had just been 
