No. 2 — Continued 
R. P. CowLES. Stimuli produced by light and by contact with solid walls as 
factors in the behavior of Ophiuroids. Thirteen figures 387 
Edwin G. Conklin. The effects of centrifugal force upon the organization 
and development of the eggs of fresh water pulmonates. Forty-seven 
figures 417 
Henry F. Nachtrieb. The primitive pores of Polyodonspathula (Walbaum). 
Twelve figures 455 
No. 3. NOVEMBER 
Seitaro Goto. On two species of Hydractinia living in symbiosis with a her- 
mit crab. Twenty-three figures 469 
Hubert Lyman Clark. The development of an apodous holothurian (Chiri- 
dota rotifera). Six figures 497 
H ENRY L. OsBORN. On the structure of Cryptogonimus (nov. gen.) Chyli (n. 
sp.), an aberrant distome, from fishes of Michigan and New York. Seven 
figures 517 
H. V. Wilson. A study of some epithelioid membranes in monaxonid sponges. 
Twenty-one figures 537 
Charles Wilson Greene. An experimental determination of the speed of 
migration of salmon in the Columbia River. Two figures 579 
T. H. Morgan. Cytological studies of centrifuged eggs. One hundred and 
eighteen figures 593 
No. 4. DECEMBER 
David H. Tennent. Variation in Echinoid plutei. Twenty-four figures 657 
Duncan S. Johnson. Studies in the development of the Piperaceae. Seventy- 
one figures 715 
Robert P. Bigelow. A comparison of the sense organs in Medusae of the 
family Pelagidae. Thirty-eight figures 751 
Ross Granville Harrison. The outgrowth of the nerve fiber as a mode of 
protoplasmic movement. Three plates and three figures 787 
George C. Price. The structure and function of the adult head kidney of 
Bdellostoma stouti. Four figures 849 
J. Frank Daniel. Observations on the period of gestation in white mice 865 
