Gatty Marine Laboratory, St. Andrews. 155 
(four on one and three on other side) are longer and more 
slender, and are distinctly moniliform, A rounded process 
behind them on each side represents the lateral lobes of the 
collar, and a slightly opaque curved area on the anterior 
region probably indicates the alar membrane. 
The buds appear to leave the nurse-stock when six pairs 
of auterior bristles are present, viz., the first pair which 
project horizontally and five behind these, the alar membrane 
being narrower behind than in front, and developing from 
before backward. The branchial filaments have pinne and 
terminal processes. The body is comparatively short and 
wide, the anterior and posterior regions being nearly equal 
in length, A part devoid of bristles occurs behind the 
anterior region, then follows ten or eleven bristled segments 
and a caudal region devoid of bristles. 
In many from Plymouth the anterior part of the posterior 
division, the seat of the male elements, is marked by numerous 
closely arranged transverse lines apparently due to trans- 
verse rows of minute red pigment-granules on the stomach ; 
yet in these the male elements at this date (8th June) had 
not attained great development, the ovigerous region behind 
being considerably in advance, as might be anticipated in 
view of the presence of the ova in the early bud. A portion 
of the tail, consisting of a variable number of segments 
(12-15 or more), being free from reproductive elements and 
presenting only the greenish blood-vessels of the gut and 
the feet. The contrast, therefore, between such specimens 
and those forwarded in March, in which month the repro- 
ductive elements were inconspicuous, though buds were 
numerous, was pronounced. In June, again, the budding 
forms had reproductive elements developed only in the bud, 
the reddish hue of which betokened the early ova, only a 
median greenish stripe, broad at the veut, indicating the 
alimentary canal in the bud ready to separate. Such subse- 
quently developed a caudal region of numerous segments. 
No uniformity appeared to ene as to the seement of the 
posterior region from which the bud sprung, ‘for example, 
SIX, seven, eight, nine, and ten bristled segments occurred. 
in a series in front of the bud, 
The sperms frequently develop in the forms from Plymouth 
a little later than the ova, none indeed appearing in the bu, 
but by-and-by they fill the non-bristled region in front of 
the ovigerous segments and bulge laterally, the region being 
thus characterized by its pallor. 
Ou the other hand, a short example having about twenty- 
five segments in the posterior region had only male elements 
in front of a part, containing ‘thirteen segments and the 
