1905.] of Permanent Forms among Chromosomes, etc. 565 



desire to publish them in the hope that other cytologists may be able to 

 throw fresh light upon the facts which we have already ascertained. 



If the testes of Triton be examined at the time when the first maiotic 

 division is abundant, groups of dividing nuclei may be found presenting the 

 appearance given in fig. 1 (Plate 24). The drawing is an accurate representation 

 of a field of such dividing cells, and upon examination it may be found that 

 the gemini (heterotype chromosomes) lie either upon young spindles or in 

 groups within cells where the nuclear membrane has only lately disappeared. 



If in such a field we consider some special form assumed by the gemini, 

 such as the U, or oc ; it will be seen that it is generally possible to find this 

 form in any individual cell we like to examine. 



So also if we take another conspicuous class of gemini which may be 

 represented thus : — £), we again find that this type also can be traced in 

 almost any individual cell we please. 



If for the time being we confine our attention to these two forms, and pass 

 from the particular field represented in fig. 1 to a large number of similar 

 fields, the conclusion is quickly forced upon us that the two forms in 

 question are really always present in all first maiotic spindle figures. We 

 soon see in fact, that the instances where one or other is not conspicuous, are 

 due to the particular gemini being turned in such a manner that they become 

 foreshortened in the line of vision, or are obscured by other gemini, either 

 totally or in part. 



But besides the two forms of gemini above considered there are in Triton 

 others. Thus we find, as cells in fig. 1 will show, gemini which present the 

 appearance of two rods either lying parallel to one another, or crossed over 

 one another, thus : — ZZ X. Again, there is a form consisting of a bent figure 

 with symmetrical thickenings which form one aspect may be represented 

 thus: — (}. Another form consists of an asymmetrical annulus with unequal 



sides, thus : — . While, lastly, we have a long and evenly thick ring, 

 thus : — 0- I 11 this way it will be seen that in the first maiotic division of 

 Triton there are to be found six varieties of gemini, and upon looking into 

 the matter, we are led to conclude that all these six varieties co-exist in 

 every instance of the first maiotic division. 



In some cases, however, it is possible to see more than one representative 

 of any particular type in one and the same cell, and upon counting the 

 maximum representation of any type found in a particular element, we find 

 in Triton this number is two. Taking each of the six classes or types of 

 gemini in turn, we find that cells may be found that show two representa- 

 tives of every one of the six classes. 



