Clare Inland Survey — ArchianneMda and Polychaeta. 47 1 1? 



resemble the crochets in shape, except that they terminate in long slender 

 points. The crochets increase in size in the posterior segments, where the 

 setae are relatively much more prominent than in the anterior and middle 

 regions, and occupy all the lateral area of the body. The distance between 

 the dorsal and ventral bundles remains fairly constant, diminishing only very 

 slightly towards the posterior end. Thus the arrangement of the setae in 

 the posterior region is intermediate between that usually associated with 

 Heterocirrus on the one hand and Chaetozone on the other. 



None of the pelagic specimens were sexually mature ; and the free-swim- 

 ming habit at night has evidently been adopted for the purpose of seeking 

 food. 



Stage B. — This stage is represented by a single specimen obtained by 

 digging in clean sand in Blacksod Bay in September. It is 11mm. long, 

 consisting of about 120 segments. The body is long and slender, and the 

 inflation of the anterior end characteristic of Stage A is not evident. The 

 anterior end resembles that of Stage A, but the eyes are darker and slightly 

 more ventral in position. The setae resemble those already described, but 

 are, on the whole, stronger, thicker, more prominent, and more numerous, 

 especially at the posterior end. In the anterior region they do not diS'er 

 from the arrangement found in Stage A. The concave side of the curved 

 blade shows the same tendency to become frayed, owing to abrasion. In the 

 posterior region there is also a close resemblance; but some of the ventral 

 divisions have each four crochets, the bifid nature of which is not so evident 

 as in those of Stage A. The lowest crochet is always bifid ; the next may 

 show a slight indication of a cleft at the tip ; and the two remaining crochets 

 have simple rounded points (fig. 29 J, a-c). The thick capillary setae of both 

 divisions taper rapidly to very fine points (fig. 29j, d). These thick setae 

 and the crochets alternate with very slender long capillary setae. The tail 

 shows a slight indication of flattening. 



Stage C. — This stage, to which the fragment described by Mcintosh also 

 belongs, is also represented by an entire specimen found in clean sand in 

 Blacksod Bay in March. It attains the relatively enormous length of -1-1 mm., 

 but consists only of 150 segments — a number not greatly exceeding that of 

 Stage B. The head bears two ventrally placed reddish-brown eyes. A 

 characteristic feature is the marked flattening of the posterior part of the 

 body, which is only slightly indicated in Stage B. The setae are much more 

 numerous than in Stages A and B, but have the same arrangement in two 

 iows, one consisting of thick flattened setae, the other of long slender 

 cylindrical setae. In the posterior segments there are 18-25 setae in each 

 bundle. The ventral bundles contain 6-7 crochets, terminating in simple 



