238 



NATURAL HISTORY. 



OUTHOXIA FAB1UCII. 



his scoop, and then mould and smoothan it with his trowel." These organs, described above, receive 

 the pellets of mud which the animal mixes up " with an adhesive secretion, furnished probably by 

 the collar of the cephalic segment, and by the organs just mentioned. It is thus rendered consistent 

 and tenacious, and fit to be employed in raising the edge of the tube. To that position the material 

 is raised by the tongue and trowels, aided by a general elevation of the head ; and it is fashioned 

 into shape by the same scoop and trowels, curved over the exterior circumference as far as they can 

 be stretched, and smoothed and polished by their motions, while clasping it with their pressure ; 

 and thus the tube is built up." When clear and perfect, says Daly ell, this tube bears the narrowest 

 resemblance to a tube of caoutchouc manufactured by human art. 



The branchial plumes are the most striking part of the structure of this worm, and ah enumera- 

 tion of their parts may well fill us with wonder and admiration. " If the plume of an adult," says 



Sir John Dalyell, "displays eighty branchiae, 

 with five hundred cilia on each side, here are 

 no less than forty thousand organs endowed with 

 voluntary, distinct, and independent action. So 

 many other parts are alike privileged in their own 

 peculiar motion without the participation of the 

 rest, that it is no exaggeration to affirm that the 

 will of this timid, lowly, defenceless creature is 



fulfilled through the control of fifty thousand living parts." None of the Annelids, we are told by 

 those who have studied the history of this interesting worm, is more richly endowed with the powei- 

 of repairing wounds and losses. 



One of the Sabellinse is remarkable for the fewness of its segments the same number as in 

 caterpillars and the presence of eye-spots on the front and also on the tail segment. The species 

 Ort/tonia fabricii has a body three or four lines in length, and is vermiform ; it has a small fascicle 

 of retractile bristles on each side of the segments, and the branchial tentacles are one-third of the 

 length of the body, are straw-coloured, and rise from three stalks forming two 

 dense tufts. The tube is cylindrical, and about twice the length of the body, 

 and it is placed erect, on the roots of small seaweeds (fuci}. It is made of 

 fine mud, cemented by a glutinous secretion, and lined within by a skin. If the 

 worm be removed and placed in clean water, it soon forms a new tube-skin ; and 

 when the worm has its tube formed, it is very lively, expanding its dense branchiae 

 in a wide circle. 



The larvae of this family have one zone of cilia, and have two eye- 

 spots and two ciliated auricular appendages on the back, in front of the zone. 

 Segments are proceeded by setae in the relative position, and the auricular ap- 

 pendages divide and form the four principal branchial rays, and their number 

 augments by budding. Finally, the segments and setae become developed. 



The sub-family Serpulinae have a ciliated thoracic membrane, and the 

 ventral and dorsal surfaces partly covered with cilia, and usually there is an 

 operculum at the extremity of a tentacle. They make a calcareous tube. In 

 the genus Serpula, the operculum Avhich closes the tube-end is horny and rarely 

 calcareous. 



Serpula vermicularis, or contortuplicata, inhabits a round shelly tube ? 

 tapered regularly backwards, and marked on its dorsal surface with a more 

 or less distinct keel. It is about three inches long, and its aperture is circular, 

 with an even or somewhat everted rim. Many tubes are usually found growing 

 together, adhering to some old shell, a bit of broken pottery, or a stone, all much 

 intertwined, and mutually adherent. The worm itself is only about an inch in 



length, and there is a well-marked difference between the thorax and abdominal portion. The former 

 carries on each side prominent tubercles in place of feet, which are vigorously protrusile, and within 

 which bundles of strong bristles are thrust to and fro. On the upper part, extending half across the 

 back, is a row of microscopic hooks, wielded by long, thread-like tendons, which are fixed on mechanical 



NERVOUS SYSTEM OF 

 8E11PULA CONTORTU- 

 PLICATA. 



(After Gtgenbaur.) 



a, upper, b. lower pantrlia of 

 pharynx , 6', ventral i rank ; 

 11, nerves of mouth ; and t, 

 of antenna?. 



