147 
suggests that it is possibly derived from the yellow 
lipochrome. Fauvel (C.R. Acad. Sciences, Paris, Tome 
129, p. 1273) has recently adduced evidence in support of 
this suggestion, showing that the formation of melanin 
granules may be due to a chemical modification of the 
lipochrome taking place in the interior of the cells under 
the influence of some acid. 
GENERAL ANATOMY OF THE INTERNAL ORGANS. 
(See Plate IIT.) 
The body cavity is best opened by an incision through 
the body wall along the mid-dorsal line. It often 
happens that in freshly killed specimens the middle part 
of the alimentary canal is forced out through the incision 
owing to the fact that the animal has died somewhat 
contracted, and the contents of the ccelom are under con- 
siderable pressure. At the same time a quantity of the 
ceelomic fluid will escape through the aperture. 
The ceelom is spacious and continuous from one end 
of the animal to the other. In front it is sub-divided 
transversely by three fenestrated septa, or diaphragms. 
The first of these is placed at the anterior boundary of the 
first chetigerous segment, and is inserted into the body 
wall at the level of the anterior edge of the first chetigerous 
annulus. It is perforated by some of the retractor 
muscles of the pharynx by which, in some specimens, the 
septum is pulled back ventrally, so that at first sight its 
ventral edge appears to be inserted near the posterior 
margin of the first chetigerous annulus. Further 
examination shows that the diaphragm is not obliquely 
placed, but is situated dorso-ventrally at the anterior edge 
of the annulus. The second and third diaphragms mark 
the posterior limit of the second and third chetigerous 
