492 JOSEPH STAFFORD, 



of methylen-blue, or better still in Anodon blood with a very little 

 methylen-blue stirred into it, I have had very fine stains — chiefly in 

 the posterior end. The largest and clearest belonged to the dorsi- 

 ventral parenchyma muscles, but sometimes I have had preparations 

 that showed, nearer the surface, by weaker magnification, numerous 

 blue dots, apparently the myoblasts of the outer muscle fibres. Along 

 a muscle fibre may also be found deeper staining swellings that 

 always lie with their long axis in the same direction with the fibre 

 and are, in fact, in the fibre itself. These often show a slight trans- 

 verse lineation and represent contraction-centres. Zacharias has 

 reproduced these in his drawings but not mentioned them in the text. 



Ventral disk. 



The infra-septal portion of the body is underlaid with the ventral 

 sucker apparatus (Fig. 3, 7, 2, 11, 12). The two, as I have already 

 mentioned, are in their functions so intimately related and can together 

 so far separate from the upper body parts that I have used for them 

 the term 'foot'. Their combined function is one for attachment and 

 locomotion. The infra- and supra-septal body parts are not, on ac- 

 count of the close association of the former with the ventral sucker, 

 to be considered in any sense as distinctly différent. They are only 

 partially separated by an advantageously interposed organ which , in 

 young animals, is absent, and which always leaves a direct connection 

 of the two in the posterior undifferentiated end of the animal. Above 

 I have indicated the most apparent muscles connecting sucker and 

 body. Here I shall point out the chief things in the structure of the 

 sucker itself which, beyond the general external form, has for Aspido- 

 gaster not yet been done. 



Viewed from below it appears as an ovate , fenestrated disk 

 (Fig. 13) with crenated borders. Connecting opposite indentations of 

 the borders are a series of transverse ridges which are intersected at 

 their middle points by a central longitudinal ridge which latter how- 

 ever does not pass at either end beyond the first or the last trans- 

 verse ridge. On each side of this median ridge and approximately 

 midway between it and the margin of the disk stretches in like 

 manner a lateral ridge. These two lateral ridges end in the same 

 way as the median but at the middle points of each half of the second 

 transverse ridge in front and the second last transverse ridge behind. 

 The longitudinal and transverse ridges with the raised thickened 

 margins of the disk divide the whole surface of the latter into a 



