HARRIS : CRAYFISHES GENUS CAMBARUS. 165 



which it is accomplished seems to be simply the filling in of 

 the opening, necessarily kept till the last, through the chim- 

 ney, with material brought from below. That it is brought 

 from below, and that the sealing is not merely the result of an 

 accidental contraction of the upper part of the chimney when 

 in a moist condition, is shown by the fact that in the case of 

 some chimneys (of C. diogewsf) examined the opening was 

 filled with clay of a different color from that of the surface soil 

 or that composing the remainder of tlie chimney. The process 

 of building the chimney has been described from actual ob- 

 servation only once — by Abbott. 



Concerning the purpose of the burrowing there can now be 

 no question, enabling the animal, as it does, to occupy territory 

 otherwise uninhabitable. Some species of the genus appear 

 never to resort to the habit in its limited interpretation, while 

 others, C. immunis, and to a less extent C. virilis, for example, 

 are inhabitants of ponds or streams and resort to burrowing 

 upon the drying up of the pond or the approach of winter, while 

 C. diogenes and C. gracilis have adopted this mode of life almost 

 entirely, being found in the open water during but a very small 

 part of the year. That the burrows are not for retreats while 

 the eggs are being hatched has been clearly shown. That they 

 serve as a place of protection against enemies has been sug- 

 gested. While this cannot be the primary purpose for which 

 they are formed, it may be that the burrowing species suffer less 

 from animal enemies than do some others. My impression is 

 that the percentage of mutilation in C. gracilis is less than in 

 C. imminiis or C. virilis, which do not spend so much time in 

 burrows. Burrows are almost invariably described as extend- 

 ing to tliR water in the soil,-^ and while the water is often very 

 muddy, ic enables the animal to keep its gills moist, and this 

 seems lo be all that is necessary. There are observations to in- 

 dicate that in the burrows the animals do not spend all the 

 time in the water at the bottom, but are apt to be found above 

 it.^'' The securing of food is a question which has not been 



29. I am told that travelers on the plains watch for the crayfish chimneys as the best indica- 

 tion of a suitable locality in which to dig for water. 



30. It is by no means necessary for the crayfii-h to spend all the time in water. Some of 

 the burrowing species have sometimes been reported as making long excursions overland. C. 

 blandiiHiii was taken in a log at a considerable distance from water. Astticus is said to make 

 short excursions inland sometimes. I have never been so fortunate as to observe crayfishes 

 climbing trees to escape the rising water, as they were reported by Mr. Holder as doing! 



Of Para star a\ JiostJeri, Lonuberg ('98) says: "The sides of the carapace covering the 

 branchial chambers are beset with numerous setee, each implanted at the anterior margin of a 



