560 Mr. J. E. S. Moore and Miss A. L. Embleton. [Dec. 5, 



represented in tig. 15. At this stage, and after, the loops are very long indeed, 

 stretching in some cases completely ronnd the whole nucleus, and it is, we 

 think, without doubt chiefly owing to this circumstance that their history has 

 been in general misinterpreted.* 



A comparison of tigs. 14, 15, and 16 will show that the split after 

 becoming, as in fig. 15, very conspicuous, gradually closes up again, fig. 16, 

 whilst in figs. 17 and 18 the closing process is still further completed. 

 Even in fig. 18, however, the split is in places still visible, and at fig. 19, 

 when the loops have been finally resolved into the adult gemini of the first 

 maiotic division figure, the fission is not in all cases completely lost. 



In other animals at the same stage, Periplaneta for example, the fission, 

 as has been shown in a former work,-j- is often visible throughout the whole 

 spindle figure of the first maiotic mitosis, and in such cases the origin of the 

 fission of the daughter chromosomes is obvious. 



In the final stages of the prophase in Triton (figs. 18 and 19) the gemini 

 assume the various forms characteristic of the first maiotic division, and 

 during the diaster the rings and loops break apart in the manner repre- 

 sented in figs. 21 and 22. 



As soon as the diastral V's have been formed the original longitudinal 

 split becomes here also again clearly visible (fig. 22). It is moreover quite 

 easy to show in Triton as in other cases that it is this fission which functions 

 in the final maiotic (homotype) division. 



To recapitulate (see diagram) : — In Triton it is found, when sufficient 



* As is well known, Flemming, and after him many others, originally regarded the 

 split of the spirem as opening out in lengths to form the rings and loops presented by the 

 adult so-called heterotype chromosomes, and the longitudinal fissions of the daughter 

 elements in the diaster of this division as a subsequent and independent fission. Dixon 

 (' Boy. Ir. Acad. Proc.,' vol. 3) regarded the split seen in the spirem as due to an apjDroxi- 

 mation similar to that witnessed in the formation of the gemini. Berg (' La Cellule,' 

 vol. 21), Overton, and Miyake (loc. cit.) have adopted a similar view, regarding the late 

 split in the spirem as a lingering expression of the conjugation during the formation of 

 the several gemini. At times a similar view has been taken by Strasburger {loc. cit.) and 

 others. We regard our present observations, as well as those upon numerous other forms 

 dealt with in our former paper with Professor Farmer, as incompatible with the idea 

 contained in the works of the above authors, namely, that the split in the spirem of the 

 first maiotic division is due to an approximation, and are inclined to think that this view 

 can only have originated through a confusion having been made between the conjugation 

 during the formation of the gemini and the longitudinal fission which, without any 

 doubt whatever, does take place during the spirem stage. 



Montgomery (' Biol. Bull.,' vol. 4), in the same year as ourselves (Farmer and Moore, 

 'Boy. Soc. Proc.,' 1903, loc. cit.), regarded the split in the spirem in Amphibian heterotype 

 prophases as not constituting the opening of the loop or ring of the spindle figure, and 

 the fission of the daughter diastral elements as due to the split visible in the spirem. 



t Farmer and Moore, ' Quart. Journ. Micros. Sci.,' vol. 48, loc. cit. 



