278 Memoir Sears Foundation for Marine Research 



32°F hatched in 47 days {lOl: 330). Bigelow and Welsh gave 10-15 days as the 

 probable average incubation period for the usual temperatures prevailing in the Gulf of 

 Maine during the hatching season; these seem to vary between about 46-55° F(j6: 94). 

 The newly hatched fish, transparent and very slender, vary considerably in length, 

 with a range of about 5.3-7.0 mm {2g'. 362) or about 5.0-6.0 mm {l6\ 97). The small 



Figure 68. Clupea harengus (Europe), a-d, larval stages; a 7 mm; b 10 mm; c 19 mm; d 29 mm; e young 

 fry, 41 mm. 



yolksac is absorbed in several days, when the larvae have attained a length of 8 — 10 mm; 

 no marked changes take place in the form of the body during this time. The vent is 

 situated so far back that the length posterior to it is less than a fifth of the total body 

 length, and the depth at this size is contained about 24 times in the total length. Con- 

 siderable advancement in the development of the fins was evident in larvae around 

 1 9 mm long, taken in the tow at Helgoland ; rays definitely were present in the dorsal 

 and caudal, and the caudal had a concave margin. However, the anal and pelvic fins 

 did not become differentiated until a length of about 29 mm was attained. In young 

 about 4 1 mm long, the proportionate depth of the body has increased greatly, and the 

 vent as well as the anal and pelvic fins have all moved forward ; larvae of this size are 

 said to be in the transition stage. However, this stage may be attained by the spring fish 

 at a length of 31-44 mm, and by the fall fish at 44-60 mm (29: 363-366, figs. a-g). 



