114 Gates, Tetraploid Mutants and Chromosome Mechanisms. 



intestine in the two races gave the result 1 : 2.7. while for the 

 abdominal region of the intestine it was 1 : 3.5, and for the optic 

 ganglia 1 : 2.2. 



The average length of the metanauplius of u nival ens was 

 0.53 mm, and of bivalens 0.70 mm. The relative length of the 

 larvae of the two races in four different stages was also found to 

 be as 1 : 1.3, and these differences in size are said to be equivalent 

 to the differences in the salinity of the water in which they live. 



Artom concludes that the quantity of chromatin in the cells 

 of bivalens is more than double that in univalens, but the "area" 

 of the nuclei and cells is directly proportional to the quantity of 

 chromatin; the number of cells being approximately the same 

 in both. 



In an interesting paper which was overlooked, C. Miiller (1909) 

 has described the chromosomes of three species of Yucca; Y. gua- 

 temalensis Back., 1". aloi folia L. and Y. Draconis Torr. In all 

 three species there are five pairs of large chromosomes, varying in 

 length, and 44 46 small, globular ones, making a total of 54 or 56. 



In a later paper (1912) Miiller has studied the chromosomes 

 in a large number of genera of Liliaceae and Amaryllidaceae. The 

 numbers run from 10 12 (2 X) in four genera, to 14 in Aloe 

 Hanburyana, 16 in Qaltonia candicans and Hyacinthus orientalis, 

 16 18 in Haemanthus, 18 in Chionodoxa, 20 in Amaryllis, Bruns- 

 wigia, Veltheimia and (?) Scilla, 22 in Nerine, 26 in Bulbine annua, 

 30 32 in Eucomis bicolor, 32 34 in Listera ovata (cf. 32, Rosen- 

 berg, 1905), 36 38 in Muscari, 54 in Albnca fastigiata, 56 (?) in 

 Yucca, and about 60 in Beschornia superba. Accurate measurements 

 of many of these chromosomes are given. From these results it 

 is evident that the chromosomes of the two families are, or have 

 been, in a state of flux, and it is fairly obvious that the high 

 chromosome-numbers came from the transverse segmentation of 

 certain pairs. These formed a varying number of short chromo- 

 somes, while the remaining pairs retained their original condition. 

 Studies of this group have not yet been sufficiently extensive to 

 determine whether possibly the number of these small chromosomes 

 varies in different individuals, but it is possible that a condition 

 might be disclosed resembling that of the supernumerary chromo- 

 somes described by Wilson in Metapodius and other Hemipteran 

 genera. This group of plants ought to be a very favourable one 

 for studies of the chromosome behaviour in hybrids. 



Wilson (1909) has listed the chromosome numbers known in 

 the insects up to the date of his paper, with the following results: 

 In the family Pentatomidae the somatic number in different species 

 is known to range from 10 to 14, 16 and 26; the Pyrrochoridae the 

 female somatic number ranges from 12 to 14 and 24; in the Coreidae 



