CEPHALOCHORDA. 213 



The colour of these specimens varied somewhat. Those found outside Karativo 

 Paar and off Mutwal Island were a deep orange colour ; those found near Periya Paar 

 and south-west of Cheval Paar were pure white, while those from west of Cheval 

 Paar, on March 18th, were of a purplish-pink colour. 



The measurements of these specimens are recorded in Table II., pp. 223, 224. 



In length they vary considerably, from 25 millims. to 56 millims., the average being 

 41*5 millims. One specimen, XXIV., Table II., was much damaged, all the postanal 

 and one half of the part between the anus and atriopore being missing. The remainder 

 measured, however, 53 millims., giving us 70 millims. as the probable length of the 

 whole animal quite a giant amongst Acraniates. 



Out of the 58 specimens, 28 were females, and only 10 were proved to be males ; 

 the sex of 20 could not be determined owing to the absence of gonads. 



The size of the animal appears to bear a relation to the period of sexual maturity, 

 which is contrary to what Forster-Cooper (8) found for Asymmetron lucayanum. 

 Here it is the largest that have well-developed gonads and the smallest that are 

 immature. All the immature ones were under 36 millims. in length. This would show 

 that at a length of about 40 millims. the form B. belcheri becomes adult. All these 

 specimens, it may be noted, were caught at about the same time of the year and in 

 much the same locality, and there can be no question of some being taken at the 

 spawning season and others not. It must be that the larger ones only were adult 

 and the others immature. In the spirit specimens the gonads could not, in all 

 cases, be counted, owing to the opacity of the metapleural folds, but in the formol- 

 preserved specimens they were determined with ease. 



In all the specimens counted, except one, the gonads of the right side were more 

 numerous than those of the left, the average being 25 right to 23 left. The lowest 

 number was 15 (some had evidently been already shed), and the highest was 30. 



A few specimens had peculiar gonads. No. XX., Table II., had unusually small 

 gonads, though itself a large specimen ; while No. XXVI., Table II., showed a curious 

 arrangement, some of the gonads being quite small and alternating with large 

 mature ones. Late in March and early in April seems to be about the spawning 

 time of this variety in the Gulf of Manaar. 



The variation in the myotomes is striking, not so much in the total number as in 

 the distribution. The total myotomes ranged from 63 to 66, 64 being the average. 

 The commonest formula was 38, 17, 9, which agrees closely w T ith Kirkaldy's 

 figures (6), and differs considerably from Gunther's (1). The number of preatrioporal 

 myotomes varied from 36 to 39, by far the greater number, 34 out of 58, having 38. 

 The number of preanal myotomes varied from 16 to 18, 17 being the average; while 

 the postanal myotomes numbered 8 to 10, 9 being the commonest number. 



From these figures it will be seen that B. belcheri from Ceylon agrees closely with 

 those from Australia examined by Kirkaldy (6), and the two are undoubtedly the 

 same species, and not distinct forms as Miss Kirkaldy suggested. 



