548 A. C. WALTON 



true in the case of Allium and also of Amphiuma. Mulsow ('12) 

 describes ten tetrads in the prophase of the spermatocytes of 

 Ancyracanthus cystidicola, which unite to form five bivalent 

 tetrads. The idiosome, however, remains as a mono-tetrad. 

 This condition is similar to the one found by the writer (Wal- 

 ton, '16 a) in the spermatocytes of A. canis. In the oocytes of 

 A. cystidicola the same process occurs, but the idiosomes (2X 

 type) do not pair to form a bivalent tetrad; each member re- 

 mains as a mono-tetrad. 



In most of these tetrads and octads (bivalent tetrads) there 

 appears a transverse constriction, which may or may not coincide 

 with the plane of one of the maturation divisions. Haecker 

 ('95) and his pupils maintain that this transverse constriction, 

 or 'Querkerbe' (Haecker, '95, p. 586), is the forerunner of a 

 maturation division, and Haecker ('11) states that its appear- 

 ance is a proof of metasyndesis (telosyndesis) . Agar ('12) and 

 Kornhauser ('15) have both shown that the Querkerbe found in 

 the chromosomes of copepods, nematodes, various molluscs, 

 and even certain vertebrates, cannot be taken as a proof for 

 either para- or telosyndesis. Neither is the Querkerbe a definite 

 forerunner of a future maturation division. Its real origin and 

 nature are so obscure that as yet no satisfactory conclusion can 

 be reached as to its significance. In A. canis, as has been stated 

 already, the Querkerbe is not an indication of telosyndesis, nor 

 does it indicate, as will be shown later, the plane of a matura- 

 tion division. 



In A. canis, soon after the formation of the di-tetrads (fig. 24), 

 the plasmosome breaks up and finally disappears, if it has not 

 already done so. This homogeneously staining mass of achro- 

 matic material breaks up into many minute, deeply staining 

 granules, which are at first imbedded in a faintly tinged matrix, 

 but soon become scattered throughout the nucleus. Some of 

 these granules eventuall}^ penetrate the nuclear membrane and 

 emerge into the cytoplasm of the egg before losing their identity. 

 A few of them break down in situ in the nucleus, but sometimes 

 the plasmosome gradually diminishes in size without breaking 

 up into granules (fig. 25). As has been shown b}^ its staining 



