128 



The Canadian Field-Naturalist 



[Vol. XXXIV. 



while to their mother and remain inside the brood- 

 pouch, so that when such a mother animal is 

 caught, if placed in a glass of water and disturbed 

 by being touched with a stick, a stream of tiny 

 young ones will be seen leaving the mother and 

 swimming around in the water just as do the full 

 grown amphipods. The time in the summer in 

 which the birth of the first brood takes place in 

 Canada and Alaska depends somewhat on the 

 particular species and upon the latitude and longi- 

 tude. Generally, it may be said, that it takes place 

 about a month after the freshwater-ice begins to 

 melt in the spring, in the neighborhood of Ottawa 

 it happens in May; on the arctic coast west of 

 Coronation gulf. Northwest Territories, in July. 

 There seems to be an interval of two months be- 

 tween two successive broods at least during the 

 summer, (May to Sept. inclusive), and probably a 

 still longer period between the broods during the 

 winter (October to April inclusive). 



In the same way as is the case with the marine 

 forms, which await the return of the tide upon the 

 sand under moist sea-weed, so also are the fresh- 

 water Amphipods very tenacious to life. They will 

 congregate under stones, boards, etc., or be found 

 along the margin of large lakes under washed up 

 material. It is likewise interesting that certain 

 species at least are equally at home in sluggish, al- 

 most putrid water and in running creeks and clear 

 mountain lakes, and that they are found in the 

 alkali lakes of our western provinces as well as in 

 the ponds hidden in the woods all over the country, 

 and in springs as well as in arctic lakes. Their im- 

 portance as fish-food may be gathered from the 

 fact, that I have found the stomachs of trouts from 

 lakes in the arctic literally "stuffed" with these 

 Crustacea, in the same way as the marine species 

 make up the main food of fishes, seals and sea- 

 birds in the Arctic and as is also known, in more 

 southern latitudes. 



As to the detailed difference between the various 

 species of freshwater-amphipods known from Can- 

 ada and Alaska I refer the reader to C. R. Shoe- 

 maker's report (1920) and A. G. Huntsman's 

 paper (1915), mentioned in the introduction. A 

 key to the determination of all the freshwater Crus- 

 tacea (Malacostraca), occurring in North America 

 is given in Ortmann's article (1918), (see also 

 bibliography for other papers). 



Three families of freshwater amphipods occur on 

 this continent all of which are represented in Can- 

 ada, but probably only two of them in Alaska. 

 The two first families are distinguished from the 

 third (Orchestiidae) by the presence of a second- 

 ary short flagellum on the 2nd antennae (antennula), 

 and by the fact that the last pair of tail feet (uro- 

 pods)are not single, but divided into two parts (rami). 



The first family (Lysianassidae) is again easily 

 distinguished by the fact, that the 5th pair of body- 

 legs (peraeopods) are considerably shorter than the 

 preceding ones, a rather unique feature among the 

 amphipods. There is only one fresh-water genus 

 (Pontoporeia) belonging to this family recorded 

 from this continent and it is doubtful whether there 

 is more than one species, (P. ho^'i, Smith) though 

 two other species (varieties) have been recorded, 

 (P. filicornis and P. affinis). On this continent the 

 first two have so far only been found in freshwater, 

 (deeper parts of Lakes Superior, Michigan, On- 

 tario, Georgian Bay), the last named only in the 



sea. 



The second family (Gammaridae) is represented 

 upon this continent by half a dozen genera, of which 

 however only three are known from Canada, a 

 fourth has so far been found only in Alaska, and 

 the rest occur in caves, and underground wells in 

 the United States. The one Alaskan genus is a 

 small form (Synurella johanseni) which I myself 

 found in the tundra ponds at Teller, Seward Penin- 

 sula, in August, 1913. It is figured and described 

 in detail by C. R. Shoemaker (1920). It is not 

 likely to be found in Canada as it belongs to an 

 Alaskan and Eurasian genus, thus reminding one 

 strikingly of the phyllopod genus, Polyartemia. One 

 of the three genra found in Canada is Eucrang- 

 onyx, which is distinguished from the other Cana- 

 dian genus Cammarus by having the inner ramus of 

 the uropods rudimentary, and by not having the 

 tail-end (telson) nearly so deeply cleft as is the case 

 with Cammarus. The shape of Eucrangonyx is 

 more clumsy than that of a Cammarus of corres- 

 ponding size. There is only one species of Eu- 

 crangonyx (E. gracilis. Smithy in Canada, hitherto 

 known from the Great Lakes, (Superior, Michigan 

 and Huron), Georgian Bay and Bond Lake (To- 

 ronto), while in the United States it is distributed 

 from Rhode Island to Wisconsin. Outside of the 

 Great Lake system it seems to be limited to Ontario 

 and the Ottawa valley, judging from the following 

 new records: 



De Grassi Point, W. -shore of Lake Simcoe, Ont. 

 May 10, 30, 1917, E. M. Walker, coll., 6 specimens 

 (4 of these are from a large, temporary forest- 

 pool). About 30, (less than Vi cm. long) specimens 

 from ponds near Bond Lake, York County, Toron- 

 to, Ont., April 19, 1920, A. G. Huntsman, coll. 

 Collected by myself, surroundings of Ottawa, Ont.: 

 (1) McKay Lake, Rockchffe, April 13th, 1919, (1 

 small (5 mm.) immature specimen). (2) Pool-stream 

 in swamp at Deschenes Rapids, P.Q., April 20, 

 1919, 4 specimens (6-10 mm.), of which two were 

 immature, one full grown male and one mature fe- 

 male with many pink eggs ('/z mm. in diameter, 

 shape oval). (3) Fairy Lake, P.Q., May 4. 1919. 



