Gatty Marine Laboratory, St. Andrews. 55 



segments presenting only small ova. As the sections pass 

 downward from the dorsum toward the ventral aspect a 

 process appears at the posterior edge of the rounded projec- 

 tion formed by each segment. This is the first indication of 

 the segmental organ, and, in accordance with the structure 

 of the parts, it appears earliest in the terminal segments, the 

 process surrounding the cavity of the segmental organ. 

 These processes, as well as the hypoderm of the segment, are 

 outside the basement-membrane, which, with the circular 

 fibres, separates them from the longitudinal muscles in the 

 preparations. In transverse sections of the caudal region it 

 is seen that these segmental cavities pass inward and down- 

 ward, to open by a wide aperture on the ventral surface 

 (PI. VI. fig. 34, ao.) on each side of the ventral groove, and 

 the ripe ova can be followed from their inner (coelomic) 

 aperture to the wide external one. These wide tubes might 

 aptly be called, after Dr. Goodrich, coelomoducts, since they 

 transmit only the reproductive elements, which enter at the 

 space above and to the exterior of the outer ends of the 

 ventral longitudinal muscles. Besides the conspicuous 

 larger ripe ova, smaller ova occasionally occurred in the 

 canal. These segmental organs seem to be simple wide 

 passages for transmitting the ova to the exterior without the 

 complexity of structure observed in other forms. The inner 

 opening is above and to the outside of the ventral longitu- 

 dinal muscles, the canal curving round the latter to open on 

 the ventral surface below it. The ovaries are situated over 

 the ventral longitudinal muscles, the pi'oducts being shod 

 into the ccelom, in which further growth takes place. The 

 females, from November onward for some months, have a 

 bright pinkish coloration posteriorly, so that the breeding- 

 season is prolonged. 



In passing from behind forward the size of the body-wall 

 and its muscles increases, but the general arrangement of the 

 segmental organs and of the ovarian tufts is the same, the 

 external apertures being outside the shallow ventral groove 

 of the region and of the nerve-cord on each side. 



So far as could be observed, no atrophy in the wall of the 

 alimentary canal takes place in the ripe forms, and the 

 muscles of the body-wall likewise are normal. 



The Serpulids proper, in the separation of the sexes, are 

 in contrast with such as Spirorbis and Amphicora (a Sa- 

 bellid), in which Meyer observes that the anterior abdominal 

 segments are female, the posterior male ; whereas in Salma- 

 cina Giard held that this condition is reversed. 



