ORILLA STOTLER WERNER. 



are J-shaped bodies (Figs. 3, 4, 6, 7 number 38). Next in size 

 are a pair that are usually of rod-shape (Nos. 37) only slightly 

 shorter than the longest in the complex. Pairs 36, 35, 34, and 33 

 form a graduated series in which there is but little difference in 

 the lengths of the consecutive pairs (Figs. 1-7 and 43-48). 

 However, there is a greater difference between pairs 34 and 33 

 than between the other pairs. Pairs 36 and 35 are of the J-type 

 (Figs. 5, 6, and 7), and 33 and 34 are usually of rod-shape or bent 

 rods, though in some prophase cells they seem to be J's (Figs. 3, 

 7, 44 and 45). 



The J-chromosomes (Nos. 38, 36, 35) of this group are, in most 

 cases, constant in shape throughout prophase and metaphase and, 

 as far as observed, in anaphase. The three pairs of rod-shaped 

 chromosomes (37, 34, 33) assume various forms according to the 

 stage of mitosis and according to their position in the nucleus. 

 The members of the largest pair (Nos. 37) are especially interest- 

 ing in this respect. In the metaphase they are, in most cases, 

 straight rods pointed at the proximal end (Fig. 3). At times, 

 however, they appear in the form of U's (Fig. 4). If they lie 

 near the nuclear wall they bend to accommodate themselves to 

 this limitation. One or both ends may be bent (Fig. 7). Also 

 these two bodies are not always bent in the same shape in the 

 same cell but are so nearly the same in size that one may recognize 

 them among the other chromosomes with a fair degree of cer- 

 tainty. Fig. 23 shows some of the shapes that they assume. 

 There seems to be some differentiation of the chromatic material 

 near the ends of these chromosomes which gives them increased 

 flexibility at these points. This differentiation seems to be a 

 suture accompanied by a slight constriction of the chromosomal 

 wall. One of these sutures, if it is such, is near the incurved end 

 when the chromosome lies as represented at a, b, c, d, in Fig. 23. 

 The other point of differentiation is at the opposite end of the 

 chromosome and marks off a portion of the chromosome about 

 three times the length of the former end part. 



With reference to the matter of sutures and constrictions, the 

 condition found is not peculiar to the duck for such has been 

 described by many observers in both animals and plants. These 

 sutures and constrictions, it seems, may be median or at any 



