PROTULA TUBULARIA. 337 
crown, and then joins the basal plate. The great number, transparency and delicate nature 
of these hooks are characteristic features. If Wollebek’s' figure of the hook of Protula 
arctica, Hansen, is correct, it differs from the foregoing in general shape, shortness of the 
main fang, large size and small number of teeth above it; indeed, there are five times the 
number in the British form. 
The posterior hooks are smaller, but do not structurally differ from the anterior. They 
are situated on prominent lamellz along the sides of the body, and toward the tail these are 
very closely arranged. The very minute serrations on the anterior face of these hooks is 
in contrast with the condition in Protula intestinum, and even with De St. Joseph’s figure of 
P. tubularia. 
Reproduction.—The males received from Plymouth on July 8th discharged a milky cloud 
of sperms and soon died. Claparede (1870) mentions that in Psygmobranchus cecus the 
sexual elements completely filled the posterior region. In P. tubularia De St. Joseph met 
with red ova in the body-cavity. Lo Bianco (1909) procured the reddish ova in a gelatinous 
~ material near the mouth of the tube from April to August, most frequently from April to 
June. 
The tube (Plate CX XI, fig. 6d) is long, round, white, and tapered, as well as more or less 
curved. It is marked by lines of growth which probably indicate the free anterior end at 
various stages of development. ‘Those from Shetland and the Hebrides are fully 6 inches 
long. It appears to be free, for various forms are attached to it all round, such as Serpulids, 
Polyzoa, Balani, corals and Anemones. Montagu states that the smaller end is fixed, the 
rest (free) ascending at a considerable angle from the base, though rarely perpendicular. 
It keeps nearly the same diameter for a considerable distance toward the free end, showing 
that there is a limit to the size of the annelid. Occasionally the tubes are attached to each 
other. In the small littoral variety at Herm the tubes are fixed to the under surfaces of 
stones, or, when dredged, attached to the inner surfaces of bivalves. Langerhans (1884) 
mentions that, like Marion at Marseilles, he found the tubes with longitudinal ridges 
common at Madeira. The initial coil on a stone is sometimes lax, the tube rising in the 
water when an open coil or two are made. Occasionally on a shell the initial coil is close. 
The free tube is seldom straight, often curved in various ways. On a site apparently so 
congenial as the test of a large Spatangus at Naples two tubes, stead of rismg upward, 
kept almost to the tip on the surface of the test. 
It is probable that the Protula imtestmum of Lamarck and others does not materially 
differ from the present form. 
The Protula borealis of Sars may be this species. 
Claparéde (1868) found only a single Protula at Naples, viz., P. itestinum, but, two 
species of Psygmobranchus. He draws attention to the distant halves of the ganglionic cord 
in Psygmobranchus protensus, and he thinks this an indication of inferiority, especially as 
in larval Annelids such a condition is more marked than in the adult. He found three pairs 
of ganglia in the thoracic region, the largest beg the second. The ganglia are united by 
transverse commissures. In Protula the hypoderm is greatly developed on the ventral 
surface and richly vascular. He describes a pennate arrangement of the longitudinal 
1 ¢Skrift. Vid. Selsk. Krist.,’ Bd. ii, No. 18, p. 120, pl. xviii, figs, 6a and 60. 
