Pscudo-Reduction in tlie Oögenesis of Allolobophora foetida. 
155 
thein — and tliese conclusions we are able to Support in tlie oögenesis 
of Allolobophora. 
Sections of the ovary of Allolobophora show clearly successive stages 
of the breaking down of the bouquet (pachytene) stage into the typical 
resting oöcyte nncleus. The bivalent chiomosomes of the pachytene stage 
become longer, thinner and niore twisted until finally they disappear 
and we have the typical resting oöcyte nncleus. Roughly speaking we 
may say, the further the cell is removed froni the proximal end of the 
ovary, the later the stage of metamorphosis of the chromosomes. The 
metamorphosis of the bouquet stage into the resting oöcyte is demon- 
strated in scveral of the photographs of plate XI and is is clearly seen 
to be the reversed process of that described as typical of the evolution 
of the heterotype prophasc chromosomes, whether these are found to 
appear before the growth period, as in the forms above qnoted, or after 
the growth period as in Allolobophora (Photos 13 to 19). 
Photo 4 shows a typical bouquet group of chromosomes with several 
of the free ends torn aw'ay from the base, ln Photo 5 the component 
chromosomes of the bouquet are still further separated, though two of 
the bivalents on the right are attached end to end making it appear as if 
only ten chromosomes are present. 
Photos 6, 7 and 9 demonstrate the leptotene stage which in this form 
is a connecting link between the bouquet bivalents and the resting oöcytes. 
We believe that Photo 9 shows that the thin (leptotene) threads are dne 
to attenuation of the thick (pachytene) bivalents of the bouquet stage and 
that therefore in those cases in which such threads happen to run parallel 
to each other they represent two bivalents and not the approximation of 
two univalent chromosomes. Later these long threads become more twisted, 
break apart and disintegrate before the net-work of the resting oöcyte 
appears. One of these transitional stages is shown in Photo 6 and it seems 
reasonable to interpret the thin threads of this preparation in the light of 
those shown in Photo 9, though there are certain features in this prepara- 
tion that might be interpreted as a parallel conjugation of univalents. For 
example, at the extreme lower end of the mass of chromatin threads is a 
chromosome showing what appears to be the point of attachmcnt of two 
univalents. This might be interpreted as due to the longitudinal Splitting 
of the threads, the appearance at the point of attachment indicating that 
the split is not quite completed. The appearance at this point can also be 
interpreted as merely a break in the thin thread or a transverse Separation 
of the univalents, and a snbsequent contraction as the preparation dries. 
This last Interpretation is in keeping with the view that the bivalents of 
