CXX REPORT OF COMMTSSIONER OF FISH AND FISHERIES. 



WISCONSIN. 



A physical and biolog'ical investigation of Green Lake, Wis., was 

 conducted by Prof. 0. DwiglitMarsli, of Ripon College, during August, 

 September, and October, 1890, and July, 1891. As assistance was 

 rendered to Prof. Marsli by the Fisli Comaiission to the extent of sup- 

 plying him with tlie means of taking deep-water temperatures, we feel 

 justified in referring to some of the results of his inquiries, which have 

 been described in two papers.* They derive additional interest, 

 moreover, from the fact that other lakes in the same state — Geneva and 

 Mendota — have been made the subject of special studies for this Com- 

 mission by Prof. S. A. Forbes. 



The maximum deptii recorded for Green Lake, which is situated south- 

 east of the center of the State, is 195 feet. Temi)erature observations 

 were secured by Prof. Marsh down to a depth of 58 meters. A mini- 

 mum temperature of 5.28° C. was obtained in the deeper parts of the 

 lake, in July, 1891; in August, 1890, the temperature in correspond- 

 ing depths was 6.G° C. The author infers that the maximum bottom 

 temperature is reached in August, and remains practically the same 

 during the two following mouths. The surface temperature is nearly 

 uniform over all the deeper parts of the lake. Prof. Marsh states: 



Because of its depth, Green Lake resembles in the conditions controlling animal life, 

 the larger bodies of water, and might be expected to have a fauna somewhat difterent 

 from that of the shallower lakes. My collections seem to justify this expectation. 



The mollusks obtained were all littoral forms, and in most cases were 

 probably washed in from shallower water. Crustaceans are abundant, 

 although the number of species is small, only 16, including both the 

 pelagic and abyssal forms, having been discovered. " When we com- 

 pare the deep-water Crustacea of Green Lake with those of Lake Mich- 

 igan aud Lake Superior, as shown in the lis,ts published by Prof. Smith 

 and Prof. Forbes, we find a striking similarity. That this should be 

 true of the pelagic fauna is not strange," but the presence of the same 

 abyssal forms which never come to the surface is not so easily 

 explained, as there seems to be no geological evidence of any connec- 

 tion between Green Lake and either the Mississippi Basin or the Great 

 Lakes, by which these deep-water animals could have migrated to their 

 present location. 



MEXICO. 



Eeference may here be made to an expedition into Mexico during the 

 summer of 1891, on which Mr. A. J. Woolman acted as ichthyologist, 

 as his report upon the fishes was accepted for publication by the Fish 

 Commission.! The party traversed the northern and central parts of 



*0n the deep-water Crustacea of Green Lake. By C.Dwight Marsh. Trans. Wis- 

 consin Academy of Sciences, Arts, and Letters, vol. viii, pp. 211-213. 



Notes ou depth and temperature of Green Lake. Idem, pp. 215-218, 1 plate. 



t Report ou a collection of fishes from the rivers of central and northern Mexico. 

 By Albert J. Woolman. Bull. U. S. Fish Comm., xiv, for 1894, pp. 55-66, plate 2. 



