2 JO JORDAN. [Vol. VIII. 



The work embodied in this paper was carried on at Clark 

 University during the winters of 1890-91 and 1891-92, and 

 during the summers of the same years at the Marine Biological 

 Laboratory at Wood's Holl. 



I gladly avail myself of this opportunity to acknowledge 

 my great indebtedness to the University authorities for the 

 privileges accorded me, and for the readiness with which every 

 facility for work has been freely granted. I am under particu- 

 larly deep obligations to Professor Whitman, in whose labor- 

 atories my studies have been pursued, and who has constantly 

 furthered my work with inspiring suggestion and advice. 



Through the kindness of Mr. A. C. Eycleshymer I have 

 enjoyed the valuable privilege of comparison of certain stages 

 of my work with his unpublished results upon Amblystoma. 

 Such comparison has been of great service to me and I gladly 

 acknowledge my indebtedness to him. To my friends Drs. 

 Wheeler and Watase I am likewise deeply indebted for many 

 friendly courtesies. 



I. Natural History. 



The smaller North American newt or "water-lizard" {Die- 

 myctylus viridesccns, Raf.) is widely distributed^ throughout the 

 northern and eastern part of the United States, and may be 

 obtained easily and in great abundance. 



My investigations have been made chiefly upon newts col- 

 lected in the neighborhood of Worcester, Massachusetts. The 

 animals in that locality can be readily captured with blind 

 sweeps of a net in small shallow pools of a few feet in diameter, 

 and also in ponds and lakes of considerable size. They 

 frequent, for the most part, places with a soft, muddy bottom 

 and an abundance of water plants such as Anacharis, Fontinalis 

 and Ceratophylbwi ; in such spots they usually conceal them- 

 selves under fallen leaves and among the tangle of water 

 weeds. On warm, sunny days in early spring, however, they 

 bask openly in the sunshine in the shallow water close along 

 shore. They are not as a rule found in swiftly running water; 

 and in the large ponds they appear to prefer small bays and 

 coves sheltered from the wind. 



