54 d. moore, M.r>. ; ox Bucephalus Haimeanus 



branch where an egg sac had been attached, which, when emptied of 

 its contents, shrivelled to this form. The process of development 

 of this structure, which M. Duthiers somewhat obscurely describes, 

 I think I have also observed, and have thought it indicated the 

 rapid growth of a temporary structure fitted to receive its contents ; 

 nucleated cells sometimes alone, sometimes in groups, may be 

 seen in certain stages with a £ inch objective ; such cells evidently 

 running more or less in lines. Occasionally I have seen strings of 

 these cells connected together by an indefinite membranous 

 structure. One other point is mentioned by M. Duthiers, namely, 

 an occasional appearance of beading which he compares to a 

 rosary, and, if I understand what he alludes to, it has appeared to 

 me to be produced by the stretching of imperfectly developed 

 tubes during their removal from the animal ; partial tearing of 

 the structure, in my experience, invariably leads to irregular con- 

 traction in fully formed portions from the expulsion of some of the 

 contents. This description applies with equal truth to the similar 

 structure found in the mussel, which, however, has appeared to 

 me somewhat less branched, and less pronounced in its striation. 

 The contents of this tubular structure, about which I will now say 

 a few words, are, first, a number of granular balls, which I have 

 called yelk balls ; next the organism named Bucephalus Haimeanus, 

 in all stages of growth, beginning, as described by M. Duthiers, 

 as a flattened cone, and progressing through the stages figured in 

 the diagram to this, the most perfectly developed I have seen. It 

 is a rare occurrence to find a cockle exhibiting all these stages, 

 and I have invariably found that the most perfectly developed 

 forms existed when the whole structure was considerably diminished 

 in bulk, which, as I thought, indicated the gradual extrusion of 

 these organism on reaching that stage. M. Duthiers' figure 

 appears to me to have been drawn from a specimen not fully 

 developed. He describes and figures a mouth surrounded with a 

 true sucker ; this I have not been able to see as drawn by him. 

 To me it has appeared that the oral aperture was almost identical 

 in all points with such as may be seen in an Anguilhda, and the 

 only appearance at all resembling a sucking disc in relation to it 

 has been when the creature is strongly contracted, then the oral 

 lips appear somewhat withdrawn within the termination of the 

 body. But as M. Duthiers says that when the animal is strongly 

 contracted the sucking disc disappears, I am unable to say that 



