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Observations upon the Development of the Teleostean 



Brain, with especial reference to that of 



Olupea harengus. 



By 



Ernest W. L. Holt. 



(From the, St. Andrews Marine Laboratory, Scotland.) 



With Plates XXIX -XXXI and 4 Woodcuts. 



Preliminary. 



The ol)servatioris recorded in the present paper concern the de- 

 velopmental changes manifest in the; Ijrain of the Herring at each of 

 the four following stages; — viz. 



I. Newly-hatched or early larval stage, total length about ^V "'ch. 

 II. Eearly post-larval stage: approximate size == that of I. 



III. I inch stage. 



IV. Î' inch stage. 



V. The development of the pineal region ; this is treated sepa- 

 rately, and a fifth stage is introduced, viz. that of l/o inch 

 long. 



Methods. 



My specimens were hardencsd in corrosive sublimate and glacial 

 acetic acid (2 parts to 1) or in picro-sulphuric acid (KLi:iNENHKJiG's 

 solution). Others were placed at once in alcohol of 90 "/o- 



Of these methods I prefer the second, which appeared to give 

 better results than the first. The alcohol method is simple, but, 



