6o6 GRIFFIN. [Vol. XV. 



easily reduced to the type of a double rod. In its simplest 

 form this rod consists of slender halves terminating at each end 

 in a common knob or swelling (Fig. I, a). In drawing apart 

 in the middle, the halves may give rise to a knobbed ring 

 (Fig. I, b), and by a continuation of this process a perfect ring 

 arises, with or without one or two bead-like swellings (Fig. I, c, d). 



These rings may be open and 

 simple, or variously coiled or 

 twisted into the shape of a 

 figure 8. Occasional slender 

 rods, of extreme thinness 

 and variously coiled or bent, 

 are most readily interpreted 

 as segments of rings cut or 

 broken by the knife. In most 

 cases the granular nature of 

 both these latter rings and 

 rods is quite apparent. 

 Similar figures have been de- 

 scribed by Kastschenko ('90) 

 and Riickert ('92) in the Se- 

 lachians, Fick ('93) in the 

 Axolotl, Hacker in Copepods, 

 Farmer and Moore ('96) in 

 Lilium, and others. 



Fig. I. — Formation of chromosome groups (tetrads) 



in the prophases of the first maturation-division Shorter, mUCh thicker, and 



in 7'Aa^(U5f?«(i ; a-</, ring formation : f-;', appar- ^r*.^ .,_*.! l, 



ently single-rod type U-ldouble-r^dType ^ftCn apparently homOgeUC- 



ous rods also occur, which 

 may be very short (Fig. I, e) or longer and generally with a central 

 swelling (Fig. I,/). These may be fairly straight or variously 

 coiled, or even bent into more or less of a F shape (Fig. I, 

 g, h, i). In certain favorable cases, clear evidence of a double 

 character appear, as a distal forking or breaking apart of the 

 halves in the center (Fig. l,j). From this fact, as well as 

 from study of later and earlier stages, and analogy with 

 Zirphaea, I do not hesitate to consider all these varied forms 

 double rods in which the halves are so closely appressed 

 that the line of separation is obliterated. The central knob 



