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W. M. Wheeler 
these bodies woiild probably have long been regarded as problematic 
Ol* rudiniental. For bave not the triie testes of tbe Oligochaeta been 
similarly overlooked aud this term repeatedly and even recently 
applied to the vesiculae seminales? 
Moreover, as I bave shown, the ovaries develop and grow tili 
tbe Myzostome has reacbed its full size and thencefortb show no 
signs of tbe diminution commonly seen in rudimental or vestigial 
structures. 
Tbe small size of tbe cells cannot be taken as an indication of 
a rudimental condition of tbe organ^ since nearly all tbe tissues of 
tbe Myzostome consist of very small cells. Tbe karyokinetic figures 
so often found in tbe ovarian cells long after they bave disappeared 
from tbe otber tissues and in relatively late stages of tbe animaPs 
growtb, flatly contradict Nansen's and Beard's supposition. 
Tben, too, Beard must know that it is always more difficult 
to prove that an organ does not than that it does function. In tbis 
case also tbe bürden of proof lies vs^itb bim wbo denies. 
In bis baste to point out that my interpretation is inadequate 
Beard appears to bave lost sigbt of tbe fact that be has never yet 
shown that the general peritoneal epithelium of Mijzostoma may 
give rise to ova; and that in tbe absence of figures bis assertions 
could not pretend to any greater weigbt than tbose whicb I advanced 
in my preliminary paper. 
8) Beard makes tbe Statement (pag. 403) : »Many of tbe extreme 
cysticolous forms bave been shown to be dioecious.« Wbere has 
tbis been shown? Certainly v. Graff, wbo has given us almost 
the only observations whicb we possess on tbe Cysticola has never 
»sbown« tbis. All of tbe so-called dioecious Cysticola described by 
V. Graff are quite as readily interpreted as protandric and hystero- 
gynous bermapbrodites. 
9) Beard's Insinuation that my prediction concerning M. pulvmar 
was only made »to bolster up an argument whicb is otherwise un- 
tenable« calls for no comment after what I bave said of tbis species 
in the present paper. 
In a Lumbricus terrestris 170 mm long, the ovaries were only 1.25 mm long, 
and in a specimen of Allolohophora foetida 100 mm long, the ovaries did not 
exceed 1 mm in iength. In a M. glahrum measuring 3 mm in length, eaeh of 
the ovaries measiired ahout 0.1 mm, so that tbe length of the ovaries of the 
Myzostome compared with the length of the body is more than 30 times as large 
as those of the earthworm. 
