176 CARNEGIE INSTITUTION OF WASHINGTON. 



mg. 



Non-protein nitrogen 1,299 



Urea nitrogen 1,182 



Creatinine 13.3. 



Uric acid 0.9 



Sugar 77 



Investigations by Frank A. Potts. 

 A Case of Asexual Reproduction. 



Among the chsetopod fauna of the Tortugas in July a very small but abun- 

 dant worm was studied, belonging to the genus Ctenodrilus, which has furnished 

 classic material for the study of asexual reproduction in the past, but is so 

 sporadic in its distribution that it has not received adequate attention. The 

 species found in the Tortugas is a typical member of the "turtle-grass" 

 fauna, and is green in color. There are several (3, 4, or 5) median segments, 

 each one of which is capable of producing a new worm, and they grow in size 

 and differentiate until the parent appears as a chain of loosely connected 

 daughter zooids. Until separation actually occurs the segments do not show 

 any external signs of the secondary segmentation, with the exception of the 

 differentiation of a head, but anterior and posterior zones of proliferation are 

 established and the full number of segments is formed very soon after separa- 

 tion of the zooid. Sexual reproduction has never been observed in the genus, 

 but it is interesting that the worm disappeared from its habitat toward the 

 latter part of the month. 



Swarming of the Atlantic Palolo. 

 The Atlantic palolo (Leodice fucata) swarmed this year on July 16, the 

 day before the last quarter of the moon. Very large numbers of Heteronereids 

 swarmed at the same time, an association which does not seem to have been 

 recorded in previous years. Small Heteronereids of less than 1 cm. in length 

 were collected, but it has not been determined whether these belong to the 

 same species as the larger forms. 



Experiments on the Feeding of Teredo. 



A floating plank was taken in tow and found to be infected by Teredo. A 

 section weighing about 800 grams (containing about 70 shipworms) was cut 

 off and kept in an aquarium supplied with filtered sea-water only. Every day 

 at the same time the section of wood was changed to a new aquarium, the 

 feces discharged during the past 24 hours collected, and their dry weight 

 estimated. The experiment was continued for 10 days, and the yield of wood 

 from the burrows kept at a high level throughout. Eggs were laid by 

 many individuals, and at the end of the experiment, when many shipworms 

 were preserved, they were nearly all found to be sexually mature, while at 

 the beginning comparatively few of those examined were at that stage. 



While these experiments extended over only a short period, they tend 

 to prove that the shipworm can live, perforin its work normally, and repro- 

 duce without the possibility of using plankton as food. The ingestion of 

 wood fragments by the liver cells has already been observed by the author and 

 points unmistakably to the direct utilization of wood in the nutrition of this 

 animal. 



