202 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
They found the resting nuclei double, and sometimes the spindle was 
double and the chromosomes in two distinct groups. They believed 
there were thus represented in the cleavage nuclei maternal and 
paternal elements which remained distinct. Conklin (:01) gave the 
same interpretation to double nuclei found in Crepidula during the 
telophase of mitosis, and sometimes continuing throughout the resting 
period. ‘The nuclei were typically composed of two vesicles, each 
with a nucleolus, though the vesicles and nucleoli sometimes united 
and thus became single. ‘This condition he found in nearly all stages 
up to that of 60-cells. Hacker (:03) carried his earlier investigations 
on Copepoda further, and described the separateness of the two portions 
of the nucleus in all stages of rest and mitosis, from the fertilized egg 
to the germ mother cells. In. Triton, Rubaschkin (:05) never found 
two nucleoli in any resting nucleus; but in early cleavages he occa- 
sionally found double nuclei in resting stages, though not during 
mitosis. In the 16-cell stage and later (i. e. about the blastula stage) 
he found two vesicles in the resting stage. During mitosis the spiremes 
formed synchronously in the two vesicles, and for a short time after 
the nuclear membrane was lost the chromosomes remained in two 
ill-defined groups; but in the equatorial plate they constituted a single 
mass. In some blastulae he found no double nuclei in any cell, and in 
others there were three vesicles, which remained distinct for as long a 
time as double nuclei did. Because of the equality of the vesicles in 
size, and their synchronistic differentiation, he believes they represent 
maternal and paternal constituents. Dublin (:05) found the somatic 
nuclei of Pedicellina typically univesicular, but with two nucleoli, 
which were symmetrically placed in the nuclei. ‘This, in his opinion, 
is not an indication of the autonomy of sperm chromosomes and egg 
chromosomes. He is undoubtedly justified in refusing to accept the 
presence of paired nucleoli as evidence of autonomy, but he seems to 
me to go too far in saying, that in other forms bilobed nuclei probably 
represent only an intermediate stage in the fusion of several vesicles 
into one resting nucleus. This, of course, does occur, and possibly 
may be true in some cases where gonomery has been claimed, but 
probably ‘not in all; it is distinctly not the case in Tubularia. As 
already described, the daughter nuclei are double when in process of 
re-forming, and remain so until the next spindle is produced, and even 
then the chromosomes may be in two fairly separate groups. 
The case in Tubularia would seem to be a good example of persistent 
gonomery, but what Dublin says (p. 354) in regard to Pedicellina,— 
viz: that in early cleavages, where autonomy should be most marked, 
Cri. 
