DEPARTMENT OE MARINE BIOLOGY. I47 



Mr. E. Newton Harvey carried out a series of experiments upon the in- 

 fluence of changes of temperature in reducing or accentuating the effects of 

 the cations of the salts of sea-water upon the pulsation of the medusa Cassi- 

 opea. He concludes that the ions of these salts exert their influence upon 

 pulsation and contraction in a chemical rather than in a mechanical or physi- 

 cal manner. By adding acetic acid to the sea-water he caused the normally 

 fertilized embryo of the sea-urchin to form a double membrane even as late 

 as the blastula stage. 



Mr. Davenport Hooker found that the newly-hatched young of the logger- 

 head turtle (Thalassochelys caretta) is attracted toward the ocean by the 

 blue color of the water. If it sees the ocean through red, yellow, or green 

 glass it does not crawl toward it, but if a piece of blue glass, or even blue 

 paper, be placed anywhere within range of its vision the turtle at once crawls 

 toward it with evident excitement. 



Prof. H. S. Jennings found that in several sea-anemones the reactions 

 to stimuli are modified as a result of the past experiences of the animal. The 

 reaction to a given stimulus is not a set invariable property of the organ- 

 ism, but depends on the state of internal processes, thus the stimulus of food 

 may in the same individual produce widely diverse reactions, dependent upon 

 the past experiences and present internal state of the animal. 



Prof. H. E. Jordan finds that in echinoderms the chromosomes arise incon- 

 stantly in different species from any part of the germinal vesicle that con- 

 tains the chromatin material, and this may be either nucleolus, nuclear reticu- 

 lum, or both. The germinal spot may serve as a storehouse of material which 

 is to contribute toward the formation of the chromosomes. The chromatin 

 not so employed is reabsorbed by the cytoplasm and may serve as food. This 

 casts doubt upon the theory of the individuality of the chromosomes in in- 

 heritance. 



In Asterias forbesii and Hipponoe esculenta, during the latter half of the 

 growth period of the oocyte, all of the chromatin, with the exception of that 

 contained in the chromosomes, becomes stored in the enlarging nucleolus. 

 The chromosomes therefore do not arise out of the nucleolus, but the latter 

 merely contributes nutritive substance to them. The reduced number of 

 chromosomes is 18. 



Professor Jordan also finds that in the walking-stick insect Aplopus the 

 somatic number of chromosomes for the female is 36, the spermotogonial 

 number 35, and the number for the primary spermatocytes 18. One of these 

 is a large U-shaped chromosome which remains undivided during the pri- 

 mary spermatocyte reduction division, so that finally one half of the sperma- 

 tozoa contain 18 and the other half only 17 chromosomes. The accessory 

 chromosome is apparently a sex-determinant. 



