74 A KEVISION OF THE ASTACID.^. 



touch consists in shutting up the aperture. This is accomplished hy means 

 of several balls of mud, brought uji fiom underneath, deposited temporarily 

 on the edge of the chimney, and drawn back in close contiguity, so as to 

 intercept all communication with the external world."* 



Another account of the burrows and mounds of C. Diogenes, by R. S. 

 Tarr, has recently been printed, with diagrams, in "Nature," Vol. XXX. 

 p. 127, June 5, 1884. t Mr. Tarr's observations, like Girard's, were made in 

 the neighborhood of Washington. According to Mr. Tarr, the eggs hatch 

 about the middle of May, while the parent is living within her burrow ; but 

 Mr. P. R. Uhler tells me that during the period of incubation the female 

 goes into pools, ditches, and quiet waters along the margin of overflowing 

 creeks. Mr. Tarr believes that the chimneys result from the excavation 

 of the burrow, without implying design on the part of the crayfish. Dr. 

 C. C. Abbott,t on the contrary, is convinced that they are carefully designed, 

 since they are often built on the steeply sloping banks of ditches, where 

 the ejected balls of mud would surely roll into the ditch if they were re- 

 garded by the crayfish simply as rejected matter. In fact, an artistic tower, 

 only two inches in diameter and varying from eight to eleven inches in 

 height, is erected on the steep incline. In several such instances observed 

 by Dr. Abbott the base of the tower was provided for by levelling the ground 

 before the foundation pellets of mud were laid. Of a series of forty towers 

 observed by Dr. Abbott on the banks of a ditch, not one, in his estimation, 

 could have been the result of accident. 



As these pages are going through the press, I have received an article 

 by Dr. Abbott,§ which states that his nephew, Mr. Jos. DeB. Abbott, has seen 

 the crayfish engaged in building its chimney. The observation was made 

 in the night by the light of a candle. The crayfish was seen to emerge 

 partially from its burrow, bearing " on^ the back of its right claw a ball of 

 clay mud which, by a dexterous tilt of the claw, was placed on the rim of the 

 chimney. Then the crayfish remained perfectly quiet for a iaw seconds, 

 when it suddenly doubled up and dropped to the bottom of its burrow. 



* Girard states that Mr. T. R. Pcale informed Iiim that he had ohservcil mud chimneys, similar to those 

 built by C. Dioz/enes, in New Grenada, along the llio Magdalena, several hundred miles from the sea. This 

 observation is of interest, as indiealing the possible southward extension of Cambarus beyond the Isthmus of 

 Panama. 



f " Habits of Burrowing Crayfishes in tlio United States." 



X "Arc the 'Ciiimneys' of Burrowing Crayfish designed?" Amer. Naturalist, Vol. XVIII. p. 1157, 

 November, 1884. 



§ " How the Burrowing Crayfish works." The Inland Monthly, Vol. I. i)p. 31, .'52, Cohindjus, Ohio, 

 February, 18S5. 



