274 G. CARL HUBER 
even in the 2-cell stage, more clearly shown in the 4-cell and later 
segmentation stages, as will appear from further reconstructions 
presented. It would seem to me reasonable to assume that these 
cell masses are of such plasticity that they are molded by the 
tubal mucosa rather than they would compress the mucosa and 
maintain an inherent form. A number of segmented ova in 
presumably the 6- and 8-cell stages were removed from oviducts 
by injection and studied in warm normal salt solution, in a liy- 
ing state. In the warm normal salt solution the morula masses 
Fig. 13 Model of right oviduct of rat No. 50, 3 days, 1 hour. X 10. A short 
segment of the upper end of the uterine horn, lower part of the figure, is included. 
The fimbriated end and a part of the infundibulum removed in the drawing so 
as to expose the underlying loops; their relative position is indicated in dotted 
outline. The position of the four ova in the 4-cell stage, at the beginning of the 
last loop of the oviduct, is shown as if seen through a transparent wall. 
presented a nearly spherical form, conforming to the conventional 
illustrations of the same. In none of the sections of fixed material 
of my series was this the case. The form of the cell mass, assumed 
by the segmenting mammalian ovum in early stages of segmenta- 
tion, therefore, seems to me a question more for academic dis- 
cussion than one of fundamental importance. The right ovi- 
duct of rat No. 50 (3 days, 1 hour) was reconstructed after the 
Born method. This model is reproduced in figure 13, and 
includes the uppermost end of the uterine horn. The oviduct 
