236 E. A. ANDREWS. 



They also found adult and larval forms in 1878, by dredging 

 in water 12 to 15 feet deep near Ft. Wool, at the mouth of the 

 Chesapeake. 



Larval forms were taken at the surface in July and August. 

 These were figured and described by Rice(18) as AmpUoxus lanceo- 

 latus. 



From his statement it .appears that one specimen had been pre- 

 viously found upon the Eastern Shore of Virginia by Mr. P. K. 

 Uhler, and that it was then known that Amphioxus had previously 

 been found in Florida as well. 



Yet the first published notice of the occurrence of Acraniata in 

 Florida seems to be that of A. A. Wright (2O) who obtained large 

 numbers at Port Tampa in March 1890. Its previous discovery 

 in Florida rests upon the above statement of Kice and upon the 

 presence of specimens in the Smithsonian Museum. 



Acting upon information kindly furnished by Prof. Wright, 

 members of the Johns Hopkins Laboratory obtained large numbers 

 of adult and larval Branckiostoma caribceum at Port Tampa in 

 June 1892, which enables us to extend the distribution of this 

 species as will be seen in the summary of geographical distribution. 



From the above review it will be seen that there is but one genus 

 of Acraniates, Branchiostoma, and that the various species from 

 different parts of the world have been distinguished by the only 

 marked differential characters seen in alcoholic specimens; the 

 number and arrangement of the myotomes. Lankester (23) leaves 

 the question as to the fixity of these numerical characters, an open 

 one. So great is the difficulty of accurate counting, where the 

 terminal myotomes may be very small and vaguely demarked in 

 preserved specimens, that we do not know the limits of variation 

 in any one species. Successive counts of one specimen of B. 

 caribceum have given me such numbers as 35. 14. 9; 35. 13. 10 

 and 35. 15. 9 ; for the anal and atrial openings are also not precisely 

 localizable in preserved specimens. 



In the first appendix to this paper I have given all the enume- 

 rations of myotomes that could be found in the systematic literature 

 and in addition a considerable number made upon specimens in the 

 Smithsonian Institution and elsewhere. From a consideration of 



