September 19, 1913] 



SCIENCE 



399 



developmental stages of two species of teleosts 

 whose eggs were found in the plankton. 



Gambusia affinis is exceedingly abundant in 

 the vicinity of Beaufort in all the freshwater 

 streams entering the harbor and in the shallow 

 brackish waters. This species is of economic 

 importance as a destroyer of insects and in- 

 sect larvae. Wherever it inhabits waters in 

 which mosquitoes breed, the mosquito larvse 

 constitute its principal food. The introduc- 

 tion of these fishes into the natural waters 

 as well as into artificial ponds, aquatic gar- 

 dens, etc., in mosquito-infested regions, may 

 play an important role in the extermination 

 of these pests. 



One of the most interesting points studied 

 by Dr. Kunz was the structure of the appa- 

 ratus controlling the modified anal fin in the 

 male Gambusicu This fin functions as an in- 

 tromittent organ and is controlled by a power- 

 ful muscle which has its origin on a bony 

 process projecting ventrally from the fourth 

 to the last abdominal vertebra and the modified 

 anal spines of the first three caudal vertebras 

 and is inserted on the proximal end of the 

 anal fin rays. The third, fourth and fifth rays 

 of the fin are enlarged, greatly elongated and 

 variously curved, bearing short spines on their 

 distal portions. The interhemal which artic- 

 ulates with the third ray is enlarged and suffi- 

 ciently elongated to articulate with the two 

 anterior processes, on which the muscle con- 

 trolling the anal fin has its origin. The fifth 

 ray may be drawn forward at one side of the 

 fourth and brought into proximity with the 

 third. In this manner a groove or tube is 

 formed through which the milt is transferred 

 from the male to the female. The results of 

 this work are to be published in the near 

 future. 



On August 3, 1912, pelagic eggs of the two 

 species of teleosts were taken in the tow-net. 

 Both are spherical in form and comparatively 

 small, having a diameter of .6 to .7 mm. One 

 kind, probably those of Trichiurus lepturus, 

 are almost perfectly transparent and contain 

 no oil-globule. The other, perhaps those of an 

 engraulid, contain an oil-globule and numer- 

 ous minute pigment .snots. Eggs taken at the 



same hour on successive days were found to be 

 in approximately the same stage of develop- 

 ment. Spawning obviously occurs in the 

 evening, probably between five and eight 

 o'clock. Before six o'clock in the morning the 

 embryo is well difFerentiated. and at 36 hours 

 after spawning the little fishes are already 

 hatched. Observations on the development of 

 these two species are still incomplete. It is 

 expected that these studies will be extended 

 and the species positively identified. 



Following the work of Thompson, Johnson, 

 Tims and Dahl on the scales of the salmon 

 and English brook trout, with special refer- 

 ence to age determinations and life-history in- 

 dications, Mr. H. r. Taylor, of Trinity Col- 

 lege, Durham, N. C, undertook to verify and 

 amplify their conclusions by investigating the 

 scales of an important American food fish, 

 Cynoscion regalis being chosen. 



Age may be determined with more or less 

 accuracy by enumerating the annuli or sup- 

 posed zones of growth. Various methods of 

 bringing out these annuli clearly by stains, 

 polarized light, etc., were employed. The re- 

 sults will be explained in a paper to be pub- 

 lished shortly. 



The evidences found by Mr. Taylor do not 

 warrant the assumption that annuli are due 

 to retarded growth, as was hitherto supposed, 

 but they must be due to other causes which are 

 at present somewhat doubtful. At all events 

 it is fairly certain that if these fishes grow 

 more slowly in winter than in summer there 

 is no evidence of this on the scales. Dis- 

 tances between the annuli are found to repre- 

 sent, proportionately, the length of the fish at 

 the times of the formation of the several 

 annuli. 



The nature of the radii was also studied. 

 They were found not to be constant, but to 

 vary with the activity of the fish and with the 

 part of the body from which the scale was 

 taken. The evidence indicates that they are 

 hinges through the superior calcified layer to 

 permit the scale to bend in adaptation to the 

 motion of the body of the fish. On the head, 

 etc., where there is no flexibility, there are no 

 radii on the scales ; and their number on scales 



