Nos. IAND2.] COTYLASPIS INSIGNIS. 17 



much shorter posteriorly, as in Alacraspis according to Jagerskiold 

 '99. In life these long cells sway about with the motions of the 

 animal ; at times those in front run out into the oesophagus as in 

 Fig. 16, and at other times they point posteriorly. The cytoplasm 

 of these cells is always minutely vacuolated, and generally there 

 are large vacuoles in them. The most constant of these is 

 one located at the free end of cell ; besides it there are others at 

 deeper levels. Each cell has a large nucleus generally located near 

 its base, of a diameter of 5-7 ^, presenting a distinct membrane, 

 a large deeply staining nucleolus and a small amount of chromatine 

 in scattered grains. In a few instances I saw' nuclei manifesting 

 indications of activity, in which the nuclear membrane was want- 

 ing and in place of a clear nucleus there was a densely stained 

 granular mass. The muscular coat of the intestine does not call 

 for special remark. It consists of two layers, an inner circular 

 layer and an outer longitudinal one (see Fig. 18). The fibers 

 are scanty, especially those of the longitudinal layer. 



i. The Excretory System. 



The general arrangement of the parts of the excretory system is 

 shown on the right side of Fig. 3. The main parts are : — a median 

 single temiinal pore, two globular bladders, almost entirely separate 

 from one another, a collecting vessel running forward from the 

 bladder to the level of the pharynx, a recurrent vessel running 

 posteriorly to the level of the ventral sucker, an anterior and a 

 posterior branch from the recurrent vessel, and capillaries running 

 from flame cells to the anterior and posterior vessels. All 

 these parts are visible in living compressed specimens, but the 

 flame cells are very indistinct, owing to their small size and the 

 thickness of the cuticle through which they must be seen. The 

 bladders and collecting vessels can be studied in sections, but 

 none of the rest of the system can be seen in sections or in any 

 kind of preserved material. 



The excretory pore is single and located on the summit of a low 

 eminence at the hind end of the body (Fig. 5). The two blad- 

 ders, which are entirely free from each other elsewhere, meet here 

 and open into a short tube whose opening is the pore. The 

 bladders are oval and decidedly larger than the collecting vessel 



