Gatty Marine Lahoratoru, St. Andrews. 155 



(four on one and three on other side) are longer and more 

 slender, and are ilistinetly moniliform. A routided proeess 

 Ijeliind them on each side rei)resents the lateral IoIks of the 

 collar, and a slightly opaque curved area on the anterior 

 rejiion probably indicates the alar membrane. 



The buds appear to leave the nurse-stock when six pairs 

 of anterior bristles are present, viz., the first pair which 

 l)roject horizontally and five behind these, the alar membrane 

 beinj; narrower behind than in trout, and developing Irom 

 before backward. The branchial filaments have pinnae and 

 terminal processes. The body is com[)aratively 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, tlie 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 developmcntj 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 re|)roductive elements and 

 ])resenting only the greenish blood-vessels of the gut and 

 the feet. The contrast, therefore, between such specimens 

 and those forwarded in ]\larch, 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 vent, indicating the 

 alimentary canal in the buti ready to separate. Such siibsc- 

 quently developed a caudal region of numerous segments. 



No uniformity appeared to exist as to the segment of the 

 ])osterior 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 indited appearing in the bm', 

 but by-and-by they fill the non-bristled region in front of 

 the ovigerous segment^ and bulge laterally, the region being 

 thus characterized by its {)allor. 



On the other hand, a short exam[)le having about twentv- 

 five segments in the posterior region had only male elements 

 in front of a part, containing thirteen segments and the 



