732 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



the waters. In the two rivers referred to, the teinperatiire was nearly 

 as low as the ordiuary temperature of the springs of the region ; the 

 result probably of the very numerous springs along the banks and in 

 the beds of the rivers. The temperature of the Ausable during the two 

 days we were in the region, late in September, varied from 45'^ iu the 

 morning to 49°.3 in the evening. The Jordan River, visited in August, 

 1871, though not tested with a theruiometer, was observed to be much 

 colder than the waters of Pine Lake and River, into which it flows. 



Mr. Fitzhugh says, of the Ausable, '"The south branch of the Ausable 

 is fed by a swampy lake at its source, and there are no grayling in it 

 until you get nearly to its mouth, where it receives large springs, and 

 the water becomes pure and cold." 



If this low temperature be the controlling influence in the distribution 

 of the species, there will be a considerably more limited area suitable 

 lor its propagation than for that of the brook-trout. 



The ThymaUi of Europe are spring-spawners. Heckel and Kner say of 

 T. vulgaris of Central Europe* that it spawns at the breaking-up of the 

 ice in spring usually in March, and the young brood come out in June. 

 They, like the trout, excavate a hole in the gravel, in which they deposit 

 the eggs, and according to these authors cov^er them over with gravel 

 after the male has impregnated them. They are said to grow very rap- 

 idly, attaining a mature size in two years. 



Siebold says of the grayling of this region t that the spawning-season 

 begins iu March and may last over into April. He says that, in spawn- 

 ing fishes, the nervous activity of the skin greatly increases, and the 

 under surface of the scale becomes adherent to the skin throughout its 

 length ; probably a similar process to that observed in the California 

 salmon by Livingston Stone during the spawning season, where the 

 scales became imbedded in the epidermal sheathings.| 



Pallas says, of the species of Eastern Siberia and Kamtchatka, that 

 it deposits the spawn about the time the ice is breaking up in the rivers. 

 The Indians informed Sir John Richardson that T. signifer spawned in 

 the spring months. 



All of the species whose habits have been observed are spring- 

 spawners. 



In this ])articular, the species in the United States are similar. 



This apparent anomaly in the habits of the salmon-family is peculiar 

 to the Salmo hucho of Europe and the ThymaUi. It is probably to be 

 considered rather as a habit of late spawning, when compared with that 

 of the other species, than as earlier. 



The spawning time of the dift'erent species varies considerably as to 



* Die Siisswasserfische der ti.streichisclien Moiiarcbie bearbeitet voq Jacob Heckel 

 und Dr. Rudolf Kuer, Leipzig, Verlag vou Wilhelm Eugeltnaun, 1858. p. 245. 



t Die Siiss\vasserti.sohe vou Mittel-Envopa, bearbeitet vou C. Th. E. v. Siebold, Pro- 

 fessor der Zoologie uud vevgleicheudeu Anatoinie iu Miiucben. Mit 64 Holzschuittea 

 uud 2 farbigen Tafeln. Leipzig, Verlag von Wilhelm Eugeluiaun, 18(53. p. 270. 



X See pages 182, 190, ia Mr. Stoue's article. 



