1893.] MB. A. E. SHIPLEY OX THE GE>TJS SIPUXCULUS. 329 



are to be found. Each scale is covered externally by a thin layer 

 of cuticle, and on the upper exposed surface of the scale is a thin 

 granular layer, outside the cuticle. This also shows faint and 

 very fine striations. The papiUie all open upon this surface and 

 never upon the under surface, and it has occurred to me that this 

 outermost layer, confined to the same region of the surface, may be 

 formed by the excretion of the granular cells of the papillae. 



Plate XXV. fig. 1 represents the appearance of one of the four 

 specimens of S. indicm laid open by an incision a little to the 

 right of the median line. The alimentary canal is very slender ; 

 the mouth and oesophagus ai'e lined by cilia ; the anus is situated 

 about the level of the junction of the anterior fifth with the 

 posterior four-fifths of the total body length when fully extended. 

 The descending loop of the intestine is much thicker than the 

 ascending, anteriorly it is prolonged into several short loops. 

 The coils of the two limbs of the intestine are very loose, and I 

 did not detect any spindle muscle ; the whole ahmentary canal 

 is, however, supported by numerous muscular sti'ands given off 

 from the longitudinal muscles. 



There are two bro^^■n tubes, which open to the exterior near 

 the posterior end of the introvert. Their internal ciliated frilled 

 opening is at the same level. The diameter of the nephridia is 

 very uniform, and each is attached closely to the body-wall 

 throughout its length by a number of muscle-strands, so that the 

 great inequality of size and position which is frequently noticed in 

 these organs in other species is scarcely possible in Sii^ancalus 

 indicus. 



The heart does not extend very far down the oesophagus. It 

 was difficult to make out its exact limit, as this part of the body 

 was embedded in a caked coagulum of the ccelomic fluid. I did not 

 succeed in finding any of the branched diverticula of the dorsal 

 vessel which are not uncommon in other unarmed Gephyrea. 

 These diverticula are well shown in Sipunculus cumanensis, and a 

 section through the 03sophagas of this form is drav^Ti in Plate 

 XXVII. fig. 11. 



There are four retractor muscles which arise from about the 

 same level, almost half\^•ay between the mouth and the anus. 

 The ventral nerve cord is conspicuous ; it gives oii very numerous 

 paired nerves which pass into the skin. At the posterior end of 

 the body it is swollen into a small lump. I was not able to detect 

 any traces of generative ridges. 



The Projections in the Brain. 



The curious finger-like projections on the dorsal surface of the 

 brain in the various species of Sipunculus have received but little 

 attention on the part of zoologists. Andrefe and Ward mention 

 them, and the former states that they appear to be hollow ; this 

 is, however, not the case. 



They are comparatively conspicuous objects, and are easily seen 

 when the brain of a Sijjunculm is examined through a lens : in 



