218 



PEECY SLADEN TEUST EXPEDITION. 



more complex : at the extreme hinder end of the gill-region the bars closely resemble 

 those of A. yelagicus. 



Some numerical characters of the two species are given in the appended table. My 

 results tally with Goldschmidt's, both as to the remarkable constancy of the myotome 

 formula in A. pelagicus, and as to the variation in the number of pre-anal myotomes in 



A. valdivice. The full number appears to be attained in A. pelagicus when the animal 

 is about 7 mm. long ; the young Branchiosfoma lanceolatum is already complete in this 

 respect when it is only 3'5 mm. long, just before it begins to metamorphose. 



