1928] Wexelsen: Chromosome Numbers and Morphology in TrifoUum 367 



(fig". 4c). As to the nature of the free satellites several interpretations 

 can be given. It is possible that the fixation has failed to bring out 

 the connecting thread which is really present ; in this case the 

 phenomenon has of course no significance. Against such an interpre- 

 tation there is the fact that when the satellites appear to be free they 

 are usually found far from any chromosome, on the outside of the 

 plate, while the attached satellites usually lie in the middle of the 

 plate and are connected with the chromosome by a short and rather 

 thick thread. It may be, therefore, that the satellites sometimes 

 become free in the living cell ; in that case they may easily be lost in 

 the mitotic division, giving rise to "sports" without the satellites. 



* «' 



Fig. 4. a. Heterotypic division in pollen mother cell of T. alexandrinum; 

 h, homotypic division in same; c, diakinesis in pollen mother-cell of T. -pratense ; 

 to the right is shown a bivalent chromosome with attached satellites from 

 another diakinesis plate. Figure 4a was stained with Haidenhain's haema- 

 toxylin; figures 4b and c, with iodine-gentian- violet. 



This suggests the possibility that Karpechenko worked with strains 

 of pratense and incarnatuni which lacked the satellites. This does 

 not seem likely in the case of pratense, however, as satellites were 

 found in four strains of this species. Without making any definite 

 conclusions as to the nature of the free satellites, it seems useful to 

 point to the situation as a possibility for geneticists and cytologists 

 to bear in mind Avhen working with these species. 



In some of the diakinesis plates of pratense one bivalent was seen 

 with a pair of small bodies attached like a pair of satellites (fig. 4c). 

 The observation was made near the close of the work and no time was 

 available to follow it up by a further study of the reduction divisions. 

 It seems very probable, however, that this bivalent corresponds to the 

 one pair of satellited chromosomes to be seen in figures of somatic 

 metaphase. No instance is known to the writer in which satellites 

 have been observed attached to bivalent chromosomes in the reduction 

 division. The observation suggests that the maturation division in 

 species with somatic satellited chromosomes should be studied, with 



