25 



Among the many interesting pelagic organisms taken by the tow 

 net during the course of our work, a Tornaria , the first found in this 

 portion of the Pacific waters, has proved of special interest. 



But a small number of specimens were taken, and these all within 

 a brief period of time, between the first and the fifth of August. I am 

 quite certain they were not present in the little bay of Avalon, in 

 which our towing was mostly done , at any other time during our stay 

 on the island, since we were constantly on the lookout for them, both 

 before and after these dates. As the number of specimens captured 

 Avas so small, and as, through an unfortunate accident, several of these 

 were lost, it at first seemed best not to publish any account of the new 

 form until another summer's work should have furnished more mate- 

 rial. However , a detailed study of the few specimens preserved has 

 proved the larva to be so interesting that I believe my fellow zoologists 

 will Avelcome a description of it even though the small number of sta- 

 ges studied leave this description very incomplete. But the facts that 

 I have observed I present with confidence despite the lack of verifi- 

 cation by the examination of numerous specimens variously prepared 

 which is ordinarily so essential for rendering valid conclusions in 

 morphological work. I am thus confident because of the excellent 

 condition of the few preserved specimens which I had , and the com- 

 pleteness of the series of sections made from them. 



The living larvae were, of course, carefully studied at the sea 

 side; but most of the details of structure here described have been 

 made out by the study of preserved material. 



As to transparency, this Tornaria forms no exception to the gene- 

 ral rule for the pelagic larvae of Balanoglossus. Its movements in 

 swimming are somewhat slower than those of the New England spe- 

 cies, and the rotation of the body about its long axis as it progresses, 

 as mentioned by J. Müller in the forms described by him, and as is 

 conspicuous in the New England species, seems not to take place here; 

 at least if it does, it is to a much less extent. 



The larvae kept in aquaria readily underwent metamorphosis with 

 the usual diminution in size and loss of transparency. As I obtained 

 no young stages, I shall say nothing about the origin or development 

 of the anterior enterocoel, the proboscis vesicle, or the heart. I may 

 say, however, that the dorsal pore is single and situated a little to the 

 left of the median dorsal line as is usually the case in Tornaria. 



This Tornaria is distinguished from all others known , excepting 

 the Bahama form described first by Weldon 1887, and more re- 

 cently by Morgan 1891, by the possession of tentacles on the longi- 

 tudinal ciliated bands. 



