Euphyllopoda g 19 



with these is mainly produced by the foliaceous legs and less by the second pair 

 of antennae, while the development of the long tail (abdomen) enables them to 

 make sudden twists and jerks, like the adults. 



The above notes on the habits of the larvae were made partly by observing 

 them in the pond, and partly by keeping them alive in a glass with water. I 

 kept theni for a month, but during that period they did not attain the size of 

 those left in the pond, probably because they did not have the same food supply 

 as in their natural surroundings. Thus more larvae were collected in the same 

 pond on July 10-11, 1914; they now measured from about 5 to 10 mm. in length, 

 and there were none younger than my stage V, described on p. 53. I kept ten 

 of them, and it could now be decided, that the three largest of these were females 

 and the rest males. The former had a short ovisac, the latter small claspers 

 (second pair of antennae) . There were still a great number of larvae in the pond; 

 and they seemed to be thriving well, in spite of the fact that parts of the pond 

 were completely dried up; even places with only a gallon of water were teeming 

 with them. 



A smaller waterhole (remnant of a dried up lagoon-pond) nearby and on 

 the same level (old beach) had a water temperature of 58° F. at 6 p.m. on July 

 11. It contained, in spite of its small size, hundreds of Branchinecta paludosa 

 larvae of the same size (5-10 mm.) as the ones mentioned above. 



The four Branchinecta paludosa collected by Mr, D. Jenness in a pond 

 on Barter island, Alaska were from 15 to 20 mm. long, and represented 

 three males and one female, all mature and of the same appearance as those next 

 to be described. 



The specimens from Martin point, Alaska, July 26, 1914, measured from 

 15 to 20 mm., the full grown males being a little bigger than the corresponding 

 females. The movements of the animals were very swift, twistings of the body, 

 somersaults and jerking jumps abounding, particularly with the females when 

 I tried to catch them. I give here an outline (text figure 4a-c) of the head and 

 genitalia of one of the mature males, and of the second antennae of one of the 

 females, all side-views. The row of hooked spines or teeth on the inner side of 

 the basal segment of second antennae, the long, distal part of the latter, and the 

 terminal spines and short filament on the genitalia of the male are easily seen; 

 also the contractile nature of the second antennae of the female. In colour the 

 males were when alive, transparent, pale white-green, with the three eyes black, 

 while the foliaceous legs, brain-part and front-edge of the large claspers (2nd pair 

 of antennae) were dark green, the intestinal canal pink (copepod-content?), 

 and the ripe semen-thread white. 20 males were kept. 



The females were much more brightly coloured, a fact also known from 

 other fairy-shrimps (for instance Eubranchipus gelidus). They had a trans- 

 parent, whitish-pink main colour with black eyes. Front part of head (from 

 between the eyes) with its appendages, the back (dorsal side) and sides (from 

 above the beginning of the foliaceous legs to the last abdominal segment and the 

 base of the foliaceous legs dark purple. The tail (abdomen) behind the ovisac 

 of a dark blue-violet colour, with a white stripe (unripe egges?) on each side 

 underlying the violet colour of the tail and the purple colour of the back, 

 stretching from behind the base of the ovisac to the middle of the series of 

 foliaceous legs. Eggs in uterus ripe, 1-5 mm. in diameter of a red-brown colour. 

 Ovisac and intestine paler; unripe eggs in ovisac as a rose streak on both sides 

 of the ripe ones. There was some variation in the distribution and intensity 

 of these purple and violet colours among the 21 females I secured here, but 

 the dark-purple, streak on the dorsal side of the intestine'is particularly constant 

 and very characteristic of the mature female of this species (see p. 23). 



In several of the ponds on Herschel island I secured on August 13-14, 1914, 

 four mature males (2f cm.) and three mature females (21 cm.) of Branchinecta 

 paludosa, the biggest specimens of this species I saw during the expedition. 



26549—3 



