CEPHALOCHORDA. 211 



end of the report. The greatest length recorded is 41 millims. and the least 

 26 millims., the average for the ten being 34 - 5 millims., considerably lower than 

 Kirkaldy's average figures (6). 



Of the ten, four were males and two females, the males being of greater average 

 length, while the sex of the remaining four could not be determined. These latter 

 were those found oft' Watering Point, Galle, and one of them had a double row of 

 exceedingly minute gonads as if just developing, while the other three had none 

 whatever. This possibly gives us a clue to the spawning time of the species in 

 tropical seas. It will be noticed from Table I. (p. 222) that these four and the two 

 first males from Galle were caught at least a fortnight before the other specimens, 

 and their gonads were in various stages of development. Those caught 14 to 20 

 days later had larger and almost mature gonads, in spite of the fact that one at least 

 was considerably smaller than those caught at the earlier date. This would give us 

 the middle of March to the beginning of April as the probable spawning time of these 

 Ceylon specimens of B. lance olatum. 



In those specimens in which gonads were present they formed a double series of 

 pouches, generally equal in number on the two sides. The average number present 

 was 23 on each side, rather below Kirkaldy's average (6). The Galle specimens, 

 preserved in formol, are of a pink tint and almost transparent ; the rest, which are in 

 spirit, vary in colour from fawn to a deep orange and are much more opaque. 



The number of myotomes varied between 59-61, not a great range; but the 

 arrangement of the somites varied considerably, as Table I. shows. The preatrioporal 

 myotomes ranged from 35 to 37, the average being 36. This is rather more than 

 Kirkaldy's figures show, but Andrews (3) records several with 37 and one with 38 

 preatrioporal myotomes. The preanal myotomes varied between 11 and 14, the 

 average being 13. Nos. III. and V. on Table I. show only 11 preanal myotomes. 

 This is the lowest number recorded for the species, but repeated countings have 

 confirmed the figure. This is one more instance of the great variability in the 

 arrangement of the myotomes within a given total. The postanal myotomes vary 

 between 11 and 13, the usual figures for the species. 



The fins of these specimens agree closely with Kirkaldy's figures, especially the 

 caudal fin (fig. l), which is remarkably constant throughout. 



The ventral fin has a double series of fin rays, in fin chambers, extending its whole 

 length. The ventral fin chambers are prolonged postanally for a considerable length 

 (fig. 1), and in II., Table I., there certainly is a postanal extension of the fin rays in 

 spite of Lankestee's and Benham's statements to the contrary. The fin rays appear 

 to be better developed both in the dorsal and ventral fins in the older specimens. 



The relation ot the anterior ends of the notochord and dorsal fin is in all cases as 

 Kirkaluy figures it, i.e. the dorsal fin ends conterminously with the myotomes, 

 while the notochord is prolonged further forwards a little way. The nervous system, 

 however, does not always project beyond the dorsal fin, as in one or two of the 



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