222 CARNEGIE INSTITUTION OF WASHINGTON. 



occur in Nereis and Ceratocephale, as well as in Leodice. In the last genus the 

 process is more complicated than in the others, for only the sexual portion 

 swarms, the non-sexual portion remaining behind. Leodice fucata lives in 

 crevices in the rock, only the anterior end, carrying the gills, being protruded 

 into the water. The posterior region becomes distended with sex products, 

 and on the day of swarming is thrust out of the rock, twists with an anti- 

 clockwise movement which breaks it away at the junction between the two 

 parts of the body, and swims rapidly to the surface, where the sex products 

 are discharged. Previous to the day of swarming, the sexual region does not 

 normally come in contact with the open water, but if it accidentally does so, 

 as happens when the rock is broken open, it usually starts twisting movements 

 much like those of the normal swarming, but uncoordinated, so that the body 

 is broken into pieces. Occasionally when taken from the burrow the sex 

 region will break away and swim at the surface with a movement much like 

 that of the normal swarming. 



This sensitiveness to contact stimulus of the water, which is not shown by 

 immature individuals, becomes more marked as the animals approach matur- 

 ity, and is more evident in females than in males. It does not occur in the 

 non-sexual portions left behind in the rocks, so must in some way be connected 

 with the maturing sex products. Observations on Podarke obscura, made 

 at Woods Hole in July 1913, showed that egg-laying in this annelid is preceded 

 by the breaking down of the germinal vesicle, a process which can easily be 

 observed through the translucent body- wall. Egg-laying occurs only in the 

 early evening, and it is possible, by an examination of the entire animals, 

 at least 3 hours earlier than the time of egg-laying, to determine which will 

 lay that day. Evidently some part of the stimulus leading to egg-laying 

 comes from the activity of the egg itself. 



With a view to securing evidence on this point in the egg of Leodice fucata, 

 1 asked Dr. S. Tashiro to test with the biometer,^ the amounts of CO2 given 

 off by these eggs in different stages of maturity. I wish here to express to 

 Dr. Tashiro my appreciation of his courtesy in making the determinations. 

 His results are as follows: 



July 6, five days before swarming, a lot containing 300 egg3 gave off CO2 in an amount equiv- 

 alent to 0.000,000,000,07 gram per egg per minute. 



July 9, two individuals were selected, one of which was evidently more mature than the other. 

 The relatively immature one, tested as above, gave 0.000,000,000,08, the more mature 

 0.000,000,000,13 gram per egg per minute. 



July 11, eggs taken from the swarming female ends gave 0.000,000,000,18 gram per egg per 

 minute. All observations were made on eggs taken directly from the body cavity, 

 without any contact with sea-water. 



These observations show that a definite increase in metabolism goes on in 

 the egg as it approaches maturity, and that this must cooperate \vith the 

 various external environmental agencies, previously regarded as the sole stim- 

 ulus in determining the time of swarming. Similar internal stimuli determine 

 the time of egg-laying in non-swarming annelids. In fact, it seems very prob- 

 able that while swarming is more spectacular than more quiet egg-laying, 

 essentially similar stimulations are responsible for initiating both processes. 



Reef Corals of the Bahamas and of Southern Florida, hy T. W. Vaughan. 



BAHAMAS. 



Most of the month of May 1914 was spent in company with Dr. Mayer in 

 the Bahama Islands for the purpose of remeasuring the corals planted off Gold- 

 ing Cay in 1912 and those growing naturally which were measured at that 

 time, making an additional inspection of the Andros barrier reef, collecting 



^Tashiro, S. A new method and apparatus for the estimation of exceedingly minute quantities 

 of CO2. American Jour. Physiology, vol. 32, No. 2, 1913. 



