NOTES ON THE REARING OF THE LARV^ OF 



POLYGORDIUS APPENDICULATUS AND ON 



THE OCCURRENCE OF THE ADULT 



ON THE ATLANTIC COAST 



OF AMERICA. 



R. P. COWLES, 

 JOHNS HOPKINS UNIVERSITY, BALTIMORE, MD. 



As the larvae of Polygordius are often found in abundance at 

 Wood's Hole, Newport, Beaufort, and along the coast of Vir- 

 ginia, it seems strange that the adult Polygordius, which has 

 been found so often in Europe and which has been so well mon- 

 ographed by Fraipont, should not be taken on the coast of 

 America. 



The larvae of Polygordiits were quite abundant at Beaufort, N. 

 C., during August of 1902, and through the kindness of the 

 United States Fish Commission, I was able to collect some of 

 these and watch their development in the Commission's new lab- 

 oratory. It surprised me to find that fully developed swimming 

 larvae taken at night and measuring slightly less than I mm. in 

 length had metamorphosed by the next morning. They were 

 at this time 2 mm. in length, showing an increase of I mm. in 

 length. 



Fraipont in his monograph on Polygordius says that the trunk 

 in Polygordius a/ipendicnlatns develops inside of the primary cuticle 

 of the swimming larva, becoming folded more and more and that 

 it becomes quite long before it assumes the form which is found 

 in the later stages of development of other species. Examina- 

 tion of the larva which is found at Beaufort shows that this is 

 the case. 



In Fig. i is shown the swimming larva some time before meta- 

 morphosis. The trunk has begun to be folded and the primary 

 cuticle is still seen unbroken along its side. As this larva de- 

 velops, the trunk becomes folded more and more. This folding 

 of the trunk and the exceptional increase in the length of the 

 latter before the primary cuticle breaks, affords an explanation of 



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