AUTHOR S ABSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE OCTOBER 6. 



THE PHOTIC SENSITIVITY OF BALANOGLOSSUS 1 



W. J. CROZIER 



Agai-'s Island, Bermuda 



In view of the fact that the Balanoglossida have enjoyed so 

 considerable a morphological prominence, by reason of the affini- 

 ties to the early vertebrate stock attributed to them, it is rather 

 a matter for surprise that information regarding their behavior 

 and activities should be, as it is, conspicuously lacking. Owing 

 to the somewhat unusual condition of the nervous system in these 

 animals, moreover, their responses should, when analysed, pro- 

 vide some data of general interest. Perhaps the absence of 

 data upon the behavior of balanoglossids is in part due to the 

 difficulty of obtaining them entire and in quantities ample for 

 purposes of experimentation. Certain of the more highly modi- 

 fied balanoglossids (Ptychodera, Glossobalanus) are available at 

 Bermuda, and after devoting some time to a study of their 

 local distribution, I have been able to procure several species in 

 quantities sufficient for study. 



One of these forms, probably Ptychodera bahamensis Spengel, 

 has proved to be very plentiful, and the greater part of the ob- 

 servations here described were made upon individuals of this 

 species. The present paper aims merely to record certain 

 responses of Ptychodera when exposed to stimulation by light. 



These animals occur in localities which are at some distance 

 from the laboratory of the Biological Station, and when brought 

 to the laboratory for observation they apparently suffer some- 

 what from the disturbances incident to transportation. This is 

 particularly true in the warmer summer months. When kept 

 in aquaria, either with or without sand, they, like other enterop- 

 neusts (cf. Caullery et Mesnil, '04), exhibit hardly any active 

 movements, unless they be violently disturbed.- By careful 



1 Contributions from the Bermuda Biological Station for Research. No. 72. 



211 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 24, NO. 2 



