236 
W. M. Wheeler 
which represents a transverse section of an ovum — the contours 
of the accessory nuclei are still visible on either side of the germinai 
vesicle. They have become extended and have taken on the same 
appearance as the reticiüar cytoplasm. Within the germinai vesicle 
the stain falls to differentiate the chromatic from the achromatic 
reticulum, so that I can affirm nothing concerning the condition of the 
chromatin in this stage. Not infrequently the growing ova take up 
spermatozoa from the body-cavity and appear to digest them. This 
is shown in Fig. 13, where the fragments of the head of a Sper- 
matozoon are easily recognized by the regulär series of chromatic 
discs. This process, of course, can have no relation to fecundation, 
but appears to be due to a phagocytic tendency on the part of the 
young ova. The ova of Myzostoma^ as I shall show in auother 
paper, are never fertilized tili they are discharged into the water, 
no matter how numerous the mature and active spermatozoa which 
may occur with them in the body-cavity. 
In the stages which succeed those just described all traces of 
the accessory nuclei have disappeared. Their outlines become in- 
distinguishable from the general cytoplasmic reticulum of the ovum. 
This reticulum, at first very obscure, becomes more sharply accen- 
tuated and has more distended meshes, as the egg approaches 
maturity. Its affinity for stains is impaired and the Spaces between 
the meshes of the reticulum seem to fili with a clear liquid (Fig. 15). 
2. Myzostoma circinatiim n. sp. (PI. 10 Fig. 18). 
A single specimen of this interesting species was found cling- 
ing to the convex surface near the base of one of the arms of an 
undetermined species of Pentacrmus. The locality given on the 
Challenger label is «station 214« (south of the Philippines). The 
Myzostome was of a drab color and about 5.5 mm long. The flattened 
body was proportionally much thinner than that of M. cirriferum, 
Its edges were rolled up to a considerable extent so that their exact 
outlines could not be determined without injuring the specimen. 
They bear long cirri, presumably 10 on either side. The suckers 
were large and distinct. The tips of the parapodia were circinata 
and each parapodium bore a pointed cirrus on the mesial surface 
of its base. 
M. circinatum at first sight closely resembles v. Gkaff's M. wyville'^ 
thompsoni ('84b, PI. 6 Figs. 1 and 2), the only other described species 
