372 Mr. W.S. Perrin. On the [ May 1, 
the nucleus between the two daughter individuals being thus effected. In 
the daughter individuals the nuclear material passes through the above series 
of stages in exactly reverse order, until the spiral band characteristic of the 
adult Trypanosome is reconstituted. 

Fic. 2.—-Diagrammatic representation of the nuclear changes occurring in longitudinal 
division. 1. Nuclear band as in normal Trypanosome, form more ladder-like 
than spiral. 2. Spiral thread with chromatin masses. 3. Nuclear band 
condensed to longitudinal rod. 4. Rod segmented. 5. Stage with dumb-bell 
shaped segments. 6. Chromosomes. 7. Chromosomes divided into two in the 
longitudinal plane of the animal. The grouping into fours is due to the fact 
that the pair of chromosomes derived from one dumb-bell shaped segment 
remain close together. 
Formation of the Gametes.—The gametes are developed in the crystalline 
style of the oyster, their production being apparently occasioned by the 
melting of the style itself; as large numbers of gametes, large in the case of 
the male at any rate, are obtained, when, by keeping the oyster out of water, 
the style is caused to disappear. 
The development of the male gamete alone has been observed, but it seems 
probable that that of the female runs much the same course. 
The male gamete is produced from the indifferent form by one longitudinal 
division (fig. 3), nuclear substance being extruded from the Trypanosome near 
its middle during the division. One indifferent form thus gives rise to two 
gametes, the longitudinal division corresponding to the equation division, the 
extrusion of nuclear material to the reduction division, of higher forms. 
The nuclear band undergoes the same changes as in preparing for an 
ordinary longitudinal division, with the exception that, at the stage when 
the nucleus is in the condition of a series of dumb-bell shaped segments, 

Fic. 3.—Diagram representing some of the stages in the process of nuclear change 
occurring in the formation of the male gamete. chr., chromatin extruded at 
centre. The upper part of the Trypanosome shows the nuclear band in 
various stages of change from spiral thread to double row of dumb-bell 
shaped segments. The lower half shows the double row of chromosomes. 
