Pebruaey 16, 1906.] 



SCIENCE. 



259 



The Activity of the White Rat at Different 

 Ages: James Roldin Slonaker, Stan- 

 ford University. 



Three preliminary experiments have 

 been carried on and others are in progress 

 to determine the normal daily activity of 

 the white rat from birth to natural death 

 due to old age. The rate of growth as 

 determined by weight and the daily activity 

 as determined by the number of revolu- 

 tions of revolving cages are carefully re- 

 corded and tabulated. From the prelim- 

 inary experiments the following conclu- 

 sions may be drawn : 



1. A marked difference in daily activity 

 is noticed in rats of different ages. 



2. The very young rat and the old rat 

 are each noticeably inactive. 



3. The period of greatest activity ap- 

 pears to be when the rat has reached the 

 age of 100 days. At this age the weight 

 is but little more than half that of the 

 adult. 



4. The period of daily activity occurs al- 

 most wholly during the night-time. They 

 show little or no activity during the day- 

 time. This, I think, is due mainly to the 

 anatomical structure of the eye and to in- 

 herited tendencies. 



5. The curve of activity rises gradually 

 until the rats have reached about the age 

 of forty or fifty days, after which there is 

 a very rapid ascent. 



6. Great individual variations are mani- 

 fested, which necessitate experimenting on 

 a larger number of individuals. 



7. Owing to the premature termination 

 of these preliminary experiments, a curve 

 representing the activity from birth to 

 .death due to old age could not be con- 

 structed. Experiments now in progress 

 will furnish the data for such a curve. 



The Physiological Effects of Changes in 

 Water Density and Salinity on Fishes: 

 F. B. Sumner, College of the City; of 

 New York. 



The Poison Glands of Noturiis and ScltiU 

 beodes: H. D. Reed, Cornell University. 



The Osteology and Relationships of the 

 Percopsidce: H. D. Reed, Cornell Uni- 

 versity. 



Descriptions of a New Genus and Nine 

 New Species of Sphceromdce: Harriet 

 Richardson, Smithsonian Institution. 

 In this paper a number of new species 

 belonging to several well-known genera are 

 described, and diagnoses of genera hereto- 

 fore established are more fully drawn up, 

 together with the definition of a new genus, 

 Gassidias. The species described come 

 from off Cape St. Roque, Brazil ; off Rio de 

 la Plata, Argentine Republic; from Hako- 

 date Bay, Japan, and Cape Town, Africa. 

 The types of all are in the collection of the 

 U. S. National Museum. A few remarks 

 are offered in regard to the species of the 

 genus Tecticeps and both T. alascensis and 

 T. convexus are redescribed and additional 

 figures given. 



The Embryology of Corymorpha: Harry 

 Beal Torrey, University of California. 

 Fertilization is external; the eggs are 

 amoeboid until fertilized. Cleavage is ap- 

 proximately equal. The gastrula cavity is 

 formed between the cells of a solid endo- 

 dermie mass of planula. The latter is 

 never ciliated and has no free-swimming 

 stage, but may creep slowly. The hy- 

 dranth is formed by a transformation of 

 the distal half of the embryo; the axes of 

 the tentacles arise ^ from cells pushed out 

 from the epithelial endoderm. Rootlets 

 appear similarly. Tentacles arise accord- 

 ing to a modified quartet plan governed 

 probably in large measure by mechanical 

 conditions. Coenosarcal canals, numerous 

 in the adult, are derived from a single 

 larval cavity by ingrowth and enlargement 

 of epithelial endoderm cells. Morphal- 

 laxis plays an important role in develop- 

 ment. 



