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 {16 : 94). 

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

 with a range of about 5.3-7.0 mm (29: 362) or about 5.0— 6.0 mm (j6: 97). The small 



Figure 68. Clupea harengiis (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 

 19 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 41 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 {2g: 363-366, figs. a-g). 



