MONILIGASTER GRANDIS, A. G. B. 315 
a superficial layer of contractile substance, while the medullary 
portion consists of unmodified protoplasm and contains the 
nucleus. 
The longitudinal muscles form four longitudinal bands run- 
ning the whole length of the body. The dorsal band is semi- 
cylindrical, extending over, as nearly as possible, half the body- 
wall. The ventral band is the narrowest; it lies between the 
inner rows of seta couples, while the lateral bands lie on each 
side between the inner and outer rows of setacouples. As the 
setze are so small that they do not project through the body- 
wall, and the two setz in a couple so near together, there are 
no intersetal or accessory bands such as are present in Lum- 
bricus. Each band is built up of a number of bundles of 
cells. There is no bipinnate arrangement, the cells in each 
bundle form a solid block. The bundles lie very close to one 
another, there being only a very small amount of connective 
tissue present, and this has the nature of a granular stroma. 
The parietal layer of coelomic epithelium has the usual 
character. 
Septa.—Four of the septa are very thick, viz. v-v1, vi-vn, 
VII-VIII, and vitl-1x; the remainder are all very thin and do 
not vary! in thickness, excepting that towards the anal end of 
the body they become gradually thicker. 
The thin septa are very thin and absolutely transparent 
when fresh, and remain fairly so even in spirit. 
The arrangement of the septa in the anterior region and the 
consequent location of various organs has given me a good 
deal of trouble. The safest guide to the numbering of the 
various segments is to be found in the efferent ducts of the 
nephridia, which can with care be always traced with certainty 
up to the point where they penetrate the body-wall. The 
nerves arising from the ventral nerve-cord are also useful for 
purposes of enumeration, as they come off with absolute 
1 IT note this in contradistinction to the condition of many worms, where 
the septa which follow the thickened septa become gradually thinner and 
thinner. Here the transition is perfectly sudden, Septum vitI-rx is the 
thickest, and Septum 1x=x is as thin as any other, in the body. 
