Anatomy of Stephanoceros Eichhornii. 3 



Mr. Gosse's careful observations that the source whence this 

 secretion arises is not from a single spot, but from a consi- 

 derable area. In a transverse section (PI. I. figs. 7-9) the four 

 pairs of muscles in the foot will be seen, each interspace being 

 occupied by a cell possessing a nucleus and nucleolus, it being 

 by these that the tube is secreted. The cuticle throughout 

 the entire animal is very thin. Mr. Jackson (loc. cit.) says, 

 " The body is protected by a cuticle secreted by an under- 

 lying layer of ectoderm ic protoplasm with scattered nuclei." 

 It seems to me probable that these glandular cells belong to 

 the epidermis, which in other parts of the animal is so indis- 

 tinct that it is difficult to make it out even with high powers. 

 The " leaning over " and " the moving round on the foot as 

 a pivot " noticed by Mr. Gosse would be for two purposes — 

 the former to solidify the case, and by pressing it down cause 

 it to adhere to any foreign substance; the latter to keep a 

 central space clear, so as to allow the animal sufficient room 

 for its body when contracted. While these processes were in 

 progress the animal would be pouring out a fresh supply, and 

 so we should soon find it possessed of a tube of sufficient 

 strength to afford shelter for the occupant. 



Thinking it possible that the above conclusions might be 

 verified by comparison with other species, I cut some serial 

 sections of Melicerta ringens. It is well known that the 

 young first secrete a fine tube, and afterwards build a tube 

 of pellets round it externally. Prof. Williamson (5) says, 

 " The animal [Melicerta] attaches itself by the tail to some 

 fixed support, and develops from the skin of the posterior 

 portion of its body a thin hyaline cylinder, the dilated extre- 

 mity of which is attached to the supporting object." On 

 examining sections through the foot I was gratified to find 

 the mucous cells occupying the same position, though reduced 

 one fourth in size, but resembling in every feature those in 

 Stephanoceros. I think therefore one may safely assume that 

 the tube in both instances originates from these cells. 



Muscles. — This was the first point to which I directed my 

 attention. Dr. Hudson (loc. cit.) says, " There are consider- 

 able differences of opinion about the muscular system. Dr. 

 Leydig (loc. cit.) says that there are four muscles which rise 

 in the foot and each of which divides into a pair as it crosses 

 the trunk, and then subdivides into smaller branches as it 

 passes over the coronal cup to the base of the lobes. Mr. 

 Gosse makes them to be five pairs, and says that usually each 

 pair runs up the trunk from the foot in a line with one of 

 the arms, and then, before reaching it, divides into diverging 

 branches which, at remote points, are united to a muscular 



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