November 7, -1884.] 



SCIENCE. 



429 



has characterized the workings of the present 

 geological survey affords an example of the 

 practical value of the academy's advice which 

 should not be overlooked. While there may 

 be one or two instances in which the opinions of 

 the experts have not been justified by the re- 

 sults, we believe that the proportion of failure 

 to success will, on critical examination, turn 

 out to be less than in any other class of ques- 

 tions which the government has had to decide. 

 The only reward received bj T the men who 

 render these services is that of public appre- 

 ciation. The damage which would be done by 

 any act of the government, depriving the work- 

 ers of this little reward, is a serious matter, and 

 becomes all the more serious when we reflect, 

 that, at more than one period in the history of 

 the acaclenry, the question whether it should 

 continue its government existence hung in the 

 balance. 



LETTERS TO THE EDITOR. 



The recognition, by marine animals, of the hour 

 of the day. 



The changes produced by the tides are apparently- 

 much more important to marine animals than those 

 which are due to the rotation of the earth ; and the 

 fact that many important physiological changes are 

 regulated according to the hour of the day in these 

 organisms, as well as in terrestrial animals and plants, 

 is worthy of notice. 



The phenomenon has almost escaped the notice of 

 naturalists, although it is not at all unusual. 



Claus in 1882, and Merejkowsky in 1883, have shown 

 that the very young stages of Aequora and Obelia are 

 found only in the morning; and Merejkowsky says 

 that the successive steps in the formation of the 

 planula of Obelia follow each other with such perfect 

 regularity that each stage is met only at a definite 

 hour in the morning. This author believes that the 

 regularity is directly due to the action of light, but 

 he gives no proof of this; and observations which 

 have been made in the past three or four years at 

 Beaufort, N.C., seem to show that the regularity is 

 not due to external influences at all, but is deter- 

 mined within the organism, like the returning appe- 

 tite which tells us that the dinner-hour has come. 



The following are some of the instances which we 

 have observed at Beaufort : — 



Dr. E. R. Wilson finds that the eggs of Renilla, an 

 Alcyonarian which lives upon the bottom below low- 

 tide mark, are always laid at very nearly the same 

 hour of the day; viz., 6 a.m. In a single case spawn- 

 ing took place at 5.30, and it was never observed later 

 than 7 a.m. 



The regularity appears to be independent of tem- 

 perature, for the hour of spawning was the same in 

 cold and warm days, although the temperature does 

 have a very important influence on the rate of devel- 

 opment of the embryo. 



Dr. Wilson has observed a similar regularity in the 

 spawning of Leptogorgia; and in this case, if I re- 

 member correctly, the hour was 4 a.m. 



While Obelia lays its eggs early in the morning, I 

 find that closely related Beaufort medusae spawn at 

 night. Thus, Entima, Eirene, Turritopus, and Liriope 

 discharge most of their eggs about 8 p.m., although 

 captive specimens drop a few eggs irregularly at all 

 hours. As one hydromedusa lays its eggs early in 

 the morning, while another species lays them early 

 in the evening, the regulating influence can hardly be 

 the change of illumination. While studying the de- 

 velopment of Lucifer, a pelagic crustacean, I found 

 that sexual union occurs with great regularity be- 

 tween 6 and 8 p.m., while the eggs are laid between 

 8 and 10 p.m. ; so that the early stages can be studied 

 only between 10 p.m. and 7 a.m. 



Dr. H. H. Donaldson has observed at Beaufort, 

 that actinias of various genera are fully expanded 

 only between 5 and 6 p.m. This is true of these 

 animals in their natural homes, as well as in aquaria; 

 and experiment showed that specimens which were 

 kept in darkness expanded as promptly at the proper 

 hour as those which were exposed to direct sunlight. 



Among the animals which I have enumerated are 

 some which live at the surface, as Entima and 

 Obelia; some which live near low-tide mark, as the 

 actinias; and some which live in deeper water, as 

 Renilla. Some of them, as Lucifer, are vigorous 

 swimmers, while some, as Gorgonia, are fixed. 



Wilson's observations show that the regularity is. 

 not due to temperature, and Donaldson's experiments 

 show that it is not the effect of light. 



There is no evidence that it is due in any way to 

 the direct influence of surrounding conditions, and I 

 think we must believe that it has been established in 

 each species by natural selection, on account of its 

 advantage to the organism. 



The phenomenon is especially important to the em- 

 bryologist, for the failure to procure the fertilized 

 eggs of any animal may be due to the fact that it is 

 not captured or observed at the right hour of the day. 

 It also shows the importance of marine observa- 

 tions when the naturalist may be on duty at all hours 

 of the day and night. W. K. Brooks. 



The star-nosed mole amphibious. 



It is now more than fifteen years since Dr. Gilpin 

 announced that the star-nosed mole (Condylura cris- 

 tata) had been seen swimming, in winter, in Nova 

 Scotia; and his record, so far as I am aware, remains 

 unique. 



Mr. Napoleon A. Comeau, who lives on the north 

 shore of the St. Lawrence, near the point where the 

 river widens into the gulf, has recently been fortunate 

 enough to witness the habit in question. He writes : 

 " On the 30th of April, 1884, I saw a star-nosed mole 

 swimming under water like a muskrat. It swam 

 directly across a small brook, keeping near the bottom, 

 and moving very fast. The brook was about six feet 

 wide and two feet deep. As the mole approached the 

 hank, it turned up its snout, so that I plainly saw 

 the 'star' on its nose, and took refuge under some 

 branches where I could not get at it. Snow was still 

 deep along the banks of the stream, and there was 

 plenty of ice in places, though the mole crossed in an 

 open space." 



I have more than once caught this species in gal- 

 leries that were half full of water, and have always 

 found it most abundant in swampy situations along 

 the borders of streams, but I never had the good 

 fortune to see it swim. C. Hart Merriam. 



