110 



Nest Building and Ovulation. 



This lizard has always been given as viviparous. On the contrary 

 it builds a nest and lays eggs therein. The only time I observed the 

 nest building was on June 25th, 1894. The location was on a stony 

 clay bank at the side of an Austin street. When first seen, 6 p. m., 

 the female was excavating a tunnel at an angle of about 75° to the 

 surface of the ground, and wide and high enough to comfortably work 

 in. She dug with her front feet, pushing back the loose earth and bits 

 of stone with her hind feet until this debris was quite clear of the en- 

 trance. So absorbed was she in her work that my presence did not 

 cause any alarm. The next morning I found the tunnel neatly filled 

 again and the lizard gone. 



After carefully removing the replaced debris, the tunnel was found 

 to be seven inches deep. At the bottom, forming an L with this tunnel 

 was a narrow entrance leading into a chamber three and one-half in- 

 ches in diameter and two inches high, which was quite round except 

 for two projecting stones. Here perfectly packed in with loose earth 

 were twentyfive eggs , while again in a hole one and one-half inches 

 deep at the bottom of the tunnel, were fifteen more. Since the em- 

 bryos of one of these sets were at a considerably more advanced stage, 

 this female must have taken advantage of the excavation of another. 

 At the time of ovulation the embryo, while at an advanced stage, is 

 still not ready to hatch by probably some days or even weeks. This 

 stage will be considered in detail in a later paper on the embryology 

 of Phrynosoma, 



Authors (7, 8), give the period of gestation as high as one hundred 

 days in females kept in confinement, but while I have not complete 

 data from coition to ovulation, 1 believe that under natural conditions 

 the time of carrying the eggs is much shorter. 



A female which had laid eggs in captivity in August, 1894, be- 

 came very restless after the eggs were taken away. She tried con- 

 stantly for two or three days to get out of the vivarium at the place 

 where the wire screen had been raised to remove the eggs. Lock- 

 wood (4) gives an instance of this maternal anxiety where a female 

 attempts to distract the attention of an observer from her young. 1 



1) Girard , Stansbury's Kept. Salt Lake, p. 360. Texas. 



2)Boettger, O. , Über das Gefangenleben der gehörnten Kröteneidechse 

 [Phrynosoma cornutum Harl.) aus Mexico. Zool. Garten, p. 289 — 293. 1879. 



3) Hoffmann, W. J. , Molting of the Horned Toad [Fhrynosoma Donglasi 

 Gray). Am. Nat. Vol. 13. p. 326—327. May, 1879. 



4) Lockwood, S., Maternal Anxiety in a Horned Toad. Am. Nat. Vol. 17. 

 p. 682—683. 1883. 



