214 



Prophase. 



THOMAS H. RRYOE. 

 Metaphase. Anaphase. 



I. 2. 3. 4. 



Text-fig. 3. — Scheme of second inaluialioii division. 



1. Donble-rod clnomosome = granddaugliter cliromosonies produced in 

 anaphase of first, division. 



2. Openine: out of ionjifiludinal split established in firbt division. 



3. Se))aration of ^n-anddanuhter chromosomes. 



4. Large half-circle represents ovum; within it a frranddaughter chromo- 

 some elon^'ated into a euived lod. Smaller circles represent polar bodies ; in 

 1 a double-rod chromosome resultinr:^ from the second longitudinal split of the 

 daughter chromosomes of the first division, in 2 a single bilobed bodv, the 

 granddaughter chromosome. 



I liave given reasons for my belief that the sphere-like 

 portions of the rod can be identified through the hetero- 

 typical division, and that each submits to a division in tlie 



a 

 process ; and if we presume to call tlie first figure | it must 



b 

 necessai-ily follow that the elongated loops in the telophase of 

 the second polar spindle, and the bilobed rod in the second 



a 

 polar bod}^, must also be labelled | , and the final result is that 



b 



the apparent reduction is not confined to the first division, but 

 is maintained througliont, — in other words, that the cliromo- 

 sonies are coupled in pairs, and go through their evolutions :is 

 linked chromosomes. Now, returning to the case of Cyclops 

 brevicornis, Haecker regards each half of the double rod of 

 the first metaphase as the result of a fusion of two elements 

 end to end — so that each is bivalent, though they go through 

 their evolutions as if they were univalent rods. Thus, if each 

 half of my tetrad figure were bivalent, our results would up to 



