522 
The Ohio Naturalist. 
[Vol. VI, No. 7, 
The contraction of the spirem continues and is manifested 
not only by a shortening in length but also by a drawing together 
of the sprit glanules. This usually goes so far that the longi- 
tudinal split becomes very difficult or impossible to observe 
(figs. 6-S). The two loops destined to become the tertads now 
become more and more definite and begin to break apart (fig. G) 
sometimes becoming twisted (fig. 7) in a way that is inconceiv- 
able were they due to a longitudinal split of the original thread. 
Sometimes (fig. 8) the two arms of a loop are of different lengths 
and this again seems to me fatal to any interj)retation of their 
origin by a longitudinal split. In this stage the longitudinal 
split becomes visible again by the moving apart of the two strands 
so that we see anew the four chromatids which form the te- 
trad (figs. 8-9). So marked a contraction as is shown in figs. 7 
and 8 is not universal. Sometimes the four strands are visible 
through the whole process. Fig. 10 represents a stage but little 
later than fig. G, where the spirem has not yet broken as in that 
case though the granules are more closely ]>acked together to 
form the four elements in each of the tertads ; but the approxi- 
mation of the two sides of the loop is still incomplete in the upper 
tetrad. The chromosomes now become more compact and grad- 
ually take their position in the tetrads (fig. 11.) All traces of 
the linin thread may have disappeared by this time or the orig- 
inal linin may persist between the two tetrads as in fig. 11 
and by the attachment of its split ends show plainly which chro- 
mosomes are the result of conjugation and which of splitting. 
From a stage represented by fig. 11 it is an easy step to the ma- 
ture tetrad ready for the first division (fig. 12). The only change 
consists in a further shortening of the chromatids. 
In the process just described the ends of the loops which form 
the tetrads are connected by two double linin threads which 
twist or pass close together at a common point, corresponding to 
the bases of the two original loops. Because of their being thus 
drawn together the resultant tetrads nearly always stand at an 
angle to each other instead of extending in the same straight line, 
see especial!}’ figs. 6 and 7. This angle persists until just before 
the separation of the dyads in the first mitosis (fig. 12) and is 
very noticeable. While it cannot be regarded as positive evi- 
dence either way, it is not easy to explain such an angle on any 
assumption of double longitudinal splitting but it corresponds 
with and helps to corroborate the looping shown to take place 
in tetrad formation. 
After the tetrads are well fomied the facts of the process of 
reduction are so well known as to require no amplification here. 
From each tetrad by the two maturation divisions are passed out 
successively a dyad and a monad, leaving one monad from each 
of the tetrads to form the resulting female producleus. Since the 
