DEPARTMENT OF MARINE BIOLOGY. 179 



green species which swim among the coral heads by day bury themselves 

 under the sand at night; while, on the other hand, the red-colored fishes 

 with large eyes, such as Amia or the squirrel-fishes, remain hidden in 

 crevices by day and wander out only at night. In this connection it 

 is interesting to observe that Helland-Hansen discovered that the 

 red rays are absorbed in the upper layers of the ocean, leaving only the 

 blue and violet rays to penetrate to the greater depths. Thus the red 

 does not penetrate to the deep-sea floor, and the prevailing red color of 

 the animals there is apparently protective ; for, as there are no red rays 

 around them, they appear black. Professor Longley's observation that 

 red fishes of the shallow waters are nocturnal appears to be an interest- 

 ing extension of this principle. 



Professor H. E. Jordan obtained and successfully preserved a com- 

 plete set of embryos of the loggerhead turtle, Caretta caretta, for ana- 

 tomical study. One of these turtles laid its eggs on May 28, and the 

 young hatched on July 25 and 26. 



Dr. Edwin E. Reinke continued his observations upon the reactions 

 of the two kinds of sperm of prosobranch mollusks, finding additional 

 evidence for the view that the apyrene sperm serves as nurse-cells to 

 maintain the active eupyrene sperm. These sperm-cells appear to 

 be sensitive to changes in CO2 and to the effects of surface tension in 

 the manner explained in Dr. Reinke's report published herewith. 



As is well known to biologists, Dr. Shiro Tashiro has for several 

 years been studying the rate of metabolism as measured by CO2 pro- 

 duction in Limulus at Woods Hole, Massachusetts. He came to Tor- 

 tugas to continue these studies upon the Limulus of Marquesas, 

 Florida, making use of the ''biometer," an apparatus of extreme 

 delicacy, which he himself invented and which enables one to detect 

 minute amounts of CO2 by means of a drop of barium hydrate, upon 

 the surface of which crystals of barium carbonate form if there be car- 

 bon dioxide in the surrounding atmosphere. He found that the metab- 

 olism of the Florida Limulus is lower than that of those living at Woods 

 Hole, and that a rise or fall in temperature affects the warm-water forms 

 to a greater degree than those of Woods Hole. This is in accord with 

 the observations of Dr. Harvey and of the Director upon the tempera- 

 ture reactions of other tropical marine animals. 



Dr. Tashiro also made a study of the metabolism of Cassiopea, both 

 in natural and in diluted sea-water, and also in sea-water mixed with 

 magnesium chloride. He also found that among corals the Acropora 

 muricata, which can not withstand high temperature and is easily 

 asphyxiated, has a high rate of metabolism, whereas Siderastrea 

 radians, which is very resistant both to high temperature and to 

 asphyxiation, has a low rate of metabolism. 



He also made the very interesting observation that carbon dioxide 

 is given off into the atmosphere from the sea-water of Tortugas under 



