238 Miscellaneous. 



each hook, which has three points at one extremity, is finished off 

 with a blind hook at the opposite end, the whole of which turns upon 

 a central hinge, so that the elevation of the blind extremity, which 

 is perhaps the ordinary position in which the apparatus rests when 

 not employed, precludes the triple-pointed hook from interfering with 

 the advancement of the animal in its naturally confined abode ; but 

 the instant that the blind or protecting hook is depressed, the sharp 

 triple-pointed end becomes a most powerful agent to assist in its 

 retiring within its own abode, and is, I believe, the only external in- 

 strument belonging to the worm possessed of this capability. 



These hook-like appendages are common to most of the Tubicolce, 

 but vary in form and shape, not only with genera, but species. 



The whole internal cavity of the worm, in which the viscera exist, 

 is filled by a fluid, by means of which the animal moves ; the loss of 

 this entails destruction of motive power, to preclude which, upon 

 receiving any external wound, the animal will cut itself, by contrac- 

 tion of the annular muscles, above the injury inflicted. It also will 

 perform the same act of bisection as a means of escape from the 

 grasp of an enemy ; and this is done not only without the loss of any 

 particle of fluid, but without any appearance of discomfort or pain to 

 the animal. 



The intestinal canal is folded upon itself for about one-third of the 

 entire length of the worm, when it joins the outer walls, and is con- 

 tinued into a sort of tail or prolongated rectum. The stomach is but 

 a slight enlargement of the alimentary passage, which again contracts 

 into an oesophagus, the extremity of which is surrounded by a pre- 

 hensile muscle, which closes and forms the mouth, surrounding the 

 abdominal ridge of which are situated the tentacular cirri. 



The respiratory apparatus consists of arborescent branchial fila- 

 ments, three or four upon either side of the head. These receive the 

 blood from the abdominal artery, (which is, in truth, a respiratory 

 heart, since it injects the blood which it receives from a vascular 

 plexus into the branchial apparatus, from whence it is returned to the 

 dorsal artery,) which carries it beyond the principal viscera of the 

 animal, and then loses itself in small branches upon the walls of the 

 animal, and anastomoses with those which cover the alimentary canal. 



Above the gills are situated two ear-like appendages, which seem 

 adapted for the purpose of protecting the excessively delicate branchial 

 organs from the friction of the tube, occasioned by the creature's 

 passing to and fro. 



From the head of the animal to about the lower extremity of the 

 stomach is a mass of white granulous material, which I presume to 

 be the ovary, and on either side several ducts lead into pear-shaped 

 sacs. Within these sacs, early in February, 1 observed active motion 

 of the fluid passing as a current in one direction, excited by a power- 

 ful set of cilia. All the sacs do not seem to be in the same state of 

 advancement ; but the progress of the young creature's development, 

 as far as I was able to make out, is as follows : — Some of the particles 

 of the fluid existing within the sacs seem to unite into a nucleus, 

 which in a short time becomes the earliest formation of the new 



