94 STYLARIOIDES PLUMOSA. 



the following segments for a considerable distance four or five, and then, as a rule 



throughout more than the posterior third— three. These large forms, however, often 

 had four projecting hooks in the posterior region, and the surface-papillae were less 

 affected by sand-particles. Each is accompanied by a short, finely-tapered bristle, the 

 tip of which projects beyond the surface. The centre of each hook is opaque and striated 

 — longitudinally in the shaft, obliquely in the distal or curved region. They are hard but 

 also brittle, the extremity being frequently fractured. Though only three hooks protrude 

 externally in each foot, several (three to five) are usually in process of development in 

 the tissues. In these the tips are narrowed, whilst the basal portion is nearly twice as 

 thick as that of the perfect hook. The slender curved tip appears first. The broad 

 bases of these developing hooks strengthen the whole mass and render it stiff. Accom- 

 panying these are several developing forms with a very slender tip, or with a more 

 distinctly hook-like extremity, which is less delicate than that figured. 



Reproduction.— In a male on May 19th two long, frilled pale-pink testes, consider- 

 ably longer than the ovaries in the female, stretched from the two white organs (nephridia) 

 in front and in connection with the ventral vessel. They had only granular testis- 

 cells with nucleus and nucleolus, so that the period of maturity is probably in June or 

 July— it may be later. Both Delle Chiaje and Claparede observed the position of these 

 organs, and the latter criticised Da Costa for erroneously supposing these annelids were 

 hermaphrodite. 



In the female the ovaries had the form of elongated lobose or frilled structures of a 

 rich grass-green colour, and stretching from the white organs (nephridia) in front. The 

 ova at this time (May 19th) were small, viz. from 0*076 mm. downward, with nucleus and 

 nucleolus, and thus were far from maturity. The ovaries were permeated by numerous 

 vascular twigs of the same greenish hue as the other vessels. Dalyell l observed an 

 " ovarium, with deep grass-green ova" protruding from the body. 



Small examples differ from adults in their less dilated anterior region, and in the 

 smaller number of segments. Thus, specimens about an inch in length have from forty 

 to forty-seven or forty-eight segments. They occur in the same regions as the larger forms. 



Habits.— As a habitual inhabitant of a tube or tunnel in muddy sand, its habits are 

 comparatively sluggish, and the modified and pulpy sandy mud in the neighbourhood of 

 its tunnel seems to have undergone digestion. It rolls about in a vessel of sea-water, or 

 lies quietly with its branchiae and palpi extended, the latter being capable of great 

 elongation. Yet the annelid can wriggle or swim through the water by jerks or con- 

 tortions of the body. When the bristles anteriorly are touched it withdraws the branchiae 

 and palpi, as in many spirit-preparations— which alone were seen by Dr. Johnston. The 

 presence of other annelids, such as Polynoidae, in the vessel seem to cause it annoyance, 

 since they cling to the anterior bristles and cause it to withdraw its branchiae and palpi. 

 Moreover, the debris in a collecting-bottle coats the bristles throughout, so that it seems 

 to be best adapted for a life in a sandy or muddy tube. The long anterior bristles are 

 spread out in a fan -like manner so as to form an arch over the delicate branchiae and 

 tentacles and act both as guards and sentinels. The moment these bristles are touched 

 the branchiae contract and disappear. 



1 f Pow. Creat./ 1853, vol. ii, p. 258, pi. xviii, fig. 9. 



