176 MARINE BIOLOGICAL LABORATORY. 



as to the method of analysis employed in such a 

 process. 



Such a method we find in Caryokiiiesis. 



I will, therefore, describe the process which may be 

 termed the mechanics of nuclear division, as based on 

 my observation on Cepbalopods and Echinoderms. 



It is now agreed by many foremost investigators of 

 the subject that the essential feature of caryokinesis 

 lies in the division of the chromatic substance of the 

 nucleus among the daughter' cells, and the complicated 

 system of spindle-rays is the mechanism to effect such 

 a division. The development of a spindle clearly shows 

 this, and the following is an attempt towards a further 

 confirmation of the current view on the subject, as held 

 especially by E. van Beneden and T. Boveri. In one 

 important respect my view is entirely different from that 

 of these authors, but this difference lies more in the in- 

 terpretation of phenomena than in the facts themselves. 



First of all, I will endeavor to describe the anatomy 

 of a well-developed caryokinetic figure in the Cephalo- 

 pod ^ZZ^ upon which my observations have been chiefly 

 carried on. The question of nomenclature presents 

 some difficulty. I will use here a set of terms of a 

 simple descriptive character, descriptive of either of 

 function, of origin, or of topographic relationship of dif- 

 ferent parts. Since scientific nomenclature embodies 

 marks of the progress of our knowledge on the subject, 

 I will use, wherever convenient, such terms as have been 

 introduced quite recently, and represent, in a measure, 

 the latest phase of our information on the subject. 



The accompanying illustration (Fig. i) shows a cary- 

 okinetic figure in the blastoderm of the squid. 



