370 PROCEEDINGS OF THE ACADEMY OF [May, 



large muscles inserted on the hypodermis a little to one side of the foot, 

 passing dorsally through the body cavity and inserted with enlarged 

 ends on the hypodermis on the sides of the proventriculus (Cast's dv 1 

 and dv 2). 



(28) Depressor trunci tertius, d.tr. 3, paired, smaller than the pre- 

 ceding and placed posterior to them (Cast's dv 3). 



(29) Depressor trunci quartus, d.tr. 4, paired, behind the preceding 

 (Cast's dv 4). 



(c) Longitudinal muscles. 



(30) Levator coronte, I.e., paired, inserted posteriorly on the hypo- 

 dermis at the sides of the mastax, passing through the brain in the wall 

 of the corona, subdividing anteriorly, and ending on Sph.C. 1, G. (Cast's 

 Lml 1). 



(Cast's second visceral longitudinal muscle pair, his Llm 2, appears 

 in vorax to be hypodermal, namely my R.C. V). 



(31) Defiexor coronse, dc, paired, arising dorso-laterally by two 

 branches on the hypodermis, and passing forward to insert upon Sph.C. 

 I (Cast's Llm 3 and Llm 4). 



(d) Irregular muscles. 



(32) Contractor corome primus, c.c. 1, lying deep in the dorsal wall 

 of the corona, a muscle mth four arms (this is the one considered by 

 Mecznikow to be a nerve ganglion; it corresponds to the mb of Cast's 

 fig. 1). 



(33) Contractor coronte secundus, c.c. 2, a muscle ring lying deep in 

 the dorsal wall of the corona behind the preceding, with three pairs of 

 lateral branches, and an unpaired mecho-posterior branch (Cast's mbr). 



Cast has described the histology of these carefully, and I have 

 nothing new to add to his description. 



Nephridial system. — This (PI. XVIII, figs. 2, 3, 6) consists of the pos- 

 terior unpaired canal opening into the cloaca, the lateral canals, and 

 the ductules, the latter terminating each in a flame cell. Mecznikow 

 and Stokes have described these organs fragmentarily, and Cast very 

 fully. 



The posterior canal (PI. XVIII, figs. 2, 3) which opens into the ante- 

 rior end of the cloaca (CI.) is unpaired, thick-walled, with the lumen 

 spirally twisted. At its anterior end the lateral canals join together, so 

 that the terminal portion may be considered having originated by their 

 fusion in the mid-line. Each lateral canal passes anteriorly, then bends 

 dorsally (fig. 2), and has a very distinct lumen and a thin wall. Where 

 the lateral canal turns dorsally it greatly enlarges in diameter to form a 

 tripartite swelling; each of the three parts of this swelling possesses 



