68 
Th. II. Montgomery, jr. 
first cleavage tbere are to be distinguislied a pair of larger and of 
smaller chromosomes. Of each such pair, accordingly, it was concluded 
that one elemeut is of paternal and the otlier of maternal origin. 
The present paper attempts a more thorough examination of the 
questiou of chroinosome diflfereuce in Ascaris megalocephala hivalens 
than was given in that earlier study. 
It is in place to mention how the fignres illustrating this con- 
trihution have been inade, for in general the reader considers the 
figures the essential part of auy niorphological argument. If the 
differences in length of the chromosomes were simply variable quan- 
tities, then hy carefully drawing only those that Support the theory 
of chromosome difference and discarding all others, the figures might 
seem to prove the case and yet teil only a portion of the truth. To 
avoid this pitfali and to render the observatious as objective as possible 
I have carried out the following plan in the making of all the dra- 
wings : only such examples were drawn where all the chromosomes 
lay eutirely in the plane of the section, and such cells were drawn 
in the order of their fiuding whether they appeared to demonstrate 
chromosome difference or not. And no case was discarded that ex- 
hibited all the chromosomes in their entirety. It would have been 
desirable to have reproduced a mach larger number of cases, but 
the ones drawn are perhaps sufficient to establish the conclusions 
reached. 
1. The Sperm Chromosomes. 
The ripe Spermatozoon contains a compact nnclens that appears 
to be uever spherical, bnt always more or less elongate and con- 
stricted (PI. 2, Fig. 73). This is such a constant appearance that 
each portion of the bilobar strncture is to be looked upon as a single 
chromosome. In this Spermatozoon the chromosomes appareutly maiu- 
tain their identity even though they are more or less closely appo- 
sed. And Boveri States (1888): »in einer großen Anzahl nicht ko- 
pulierter Spermatozoeu habe ich die Zusammensetzung der homogenen 
Chromatinkugel aus zwei Halbkugeln mit vollster Sicherheit fest- 
stellen können«, and he has given several figures illustrating this 
point 1). 
q This sperm is then anotlier case to be added to that of Myzostoma 
(Wheeleu, 1897) where the chromosomes maintain morphological distinctness. 
The hypothesis suggests itself that in the compact chromatin mass of all sper- 
matozoa the chromosomes may be morphologically distinct, even though this 
condition is rarely demonstrable. 
