HARGITT: PENNARIA TIARELLA AND TUBULARIA CROCEA. 197 
growth period the chromatin was present in the form of granules (as 
in ‘Tubularia) diffused through the nucleus, and a spireme or definitive 
chromosomes were always lacking, it seems clear that the reduction 
must have occurred during early growth, or before; the conditions in 
Tubularia suggest that this happened in the odcyte just previous to the 
growth. ‘he reduction process was consequently not fully worked 
out in either Pennaria or ‘lubularia alone, but in view of the close 
relationship of these genera and their similarity in many points during 
odgenesis and development, it seems not entirely without justification 
to consider the process determined in part from each as giving an 
approximately correct picture of the whole matter in both genera. 
Tetrads in the reduced number have been found in the first matura- 
tion spindle of ‘Tiara (Boveri, ’90), Clava (Harm, :02) and Cunina 
(Stschelkanowzew, :06). In Linerges Conklin (:08) finds tetrads, 
but says nothing concerning reduction, while in Gonothyraea Wulfert 
(:02) found a reduced number of chromosomes not in tetrads. These 
forms, then, as well as Tubularia crocea and Pennaria tiarella, give 
evidence of a reduction occurring before the maturation spindle forms, 
and since the germinative vesicle contains diffuse granular chromatin 
during the growth of the egg, the reduction presumably takes place 
before growth begins. ‘The Hydromedusae thus seem to agree with 
other Metazoa in the time of reduction, but the manner of reduction 
remains undetermined. 
3. Polar-cell Formation.— In a number of Hydromedusae, includ- 
ing Pennaria and ‘Tubularia, the germinative vesicle has been thought 
to fragment and entirely disappear about the time polar cells should 
be formed. Allen (:00, p. 303) says regarding Tubularia (Parypha) 
crocea: “‘I....am forced to the conclusion that the nucleus of the 
mature egg is formed by the reorganization of the fragments of the 
nuclear matter scattered through the cytoplasm.” MHargitt (:04?, 
:04¢, :06) thinks that there may be sometimes in Pennaria, ‘Tubularia 
mesembryanthemum and other forms an apparent dispersal of the 
chromatic matter of the germinative vesicle throughout the cytoplasm, 
and Miiller (:08) maintains for Margelopsis and other species that the 
disappearance of the germinative vesicle is ‘‘absolutely complete.” 
As this author finds both chromatin bodies and maturation spindles, 
he apparently does not refer to an actual dispersal of the chromatin. 
In every egg of Pennaria and 'Tubularia which I have examined, I 
have found the nucleus in some phase of its cycle. It is often very faint, 
and is usually not accompanied by any marked concentration or 
specialization of the cytoplasm; but no sign of its fragmentation has 
