76 H. J. HANSEN. 
(Leach) and it is therefore most probable that, as to pro- 
pagation, they agree respectively with Spheroma and 
Cymodoce. Spheroma rugicauda (Leach) is mentioned 
above; S. serratum (Fabr.) has the same number of pouches 
with large slits, and all species of the genus in its restricted 
sense (see below) probably agree closely with each other. 
T examined a rather large specimen of 8. serratum with 
the young nearly full-grown, being greyish with black eyes; I 
counted ninety-one young, which occupied by far the largest 
part of the inner space of thorax and, besides, a good deal 
of abdomen, as the internal organs of the body, excepting 
musculature, were scarcely discernible. In the other genera 
of hemibranchiate Spheromine, as in Sphzroma, the brood 
is developed in internal pouches; but, nevertheless, various 
deviating features are observed. In Cymodoce pilosa 
(M.-Edw.) five pairs of large slits—first pair between first 
and second, last pair between fifth and sixth sternites—are 
observed ; the slits are placed at some distance from the 
mesial line. Of Bregmocerella Grayana (Woodw.) I have 
seen two females with the marsupium well developed, and 
the mouth-parts metamorphosed as in Cymodoce. One of 
them has no eggs; on the lower surface of thorax I found 
five pairs of small, very low sub-cylindrical tubercles placed, 
as are the slits in Cymodoce, at some distance from the 
mesial line, each tubercle with a minute aperture on the end. 
In the other female the black eyes of a rather small number 
of young are visible through the quite membranous ventral 
skin, on which it is possible, with some difficulty, to find the 
same thickenings with their central hole. That these tiny 
apertures correspond with the slits in Spheroma and 
Cymodoce is certain, but it is difficult to understand how 
the eggs can pass in, and quite incomprehensible how the 
young are able to pass out through them. I suppose that at 
the birth of the young the skin must split at the apertures, 
but perhaps some other resource may exist. As mentioned 
above, the marsupial lamellz are small and far from reaching 
each other at the mesial line in Exosphzroma (Stebb.), 
