MTTSTELUS L.EVIS. 89 



suggestion, double-stained in Ehrlich's htematoxylin and 

 Griiblo's orange, the combination which he and Mr. 

 Swinuerton had found so successful in their recent work 

 on Sphenodon (38). The two large embrj^os were cut, the 

 first one 1 f^ in thickness, and the other 10 fi in thickness. 

 The first series contained something over 3000 sections. 



After the full course of the lateral canals of the head had 

 been first traced in the sections of the 55 mm. embrjo, and 

 then in those of the 12*2 cm. one, I had them traced by dis- 

 section in two or three others of my larger remaining 

 embryos. This was at first undertaken simply as an aid and 

 guide in the preparation of the simple outline drawings 

 intended for illustration. Mr. Nomura, my assistant, under- 

 took this work, and he soon found that he could, with some 

 care and trouble, trace, not only the main lateral canals, but 

 also the ampullary canals, which latter it had been wholly 

 impracticable to trace in sections. The dra-wings made from 

 these dissections accordingly show the general course of all 

 the ampullary tubes, and the exact, or closely approximate, 

 number and position of their surface openings. They do not 

 show all the tubules of the lateral canals, and none of the 

 numerous surface openings, or pores, of these canals are 

 even indicated in the general drawings. It was found that 

 these tubules and pores could not be accurately made out 

 without much more work than the subject seemed to 

 warrant. The drawings accordingly only show, accurately, 

 those tubules that project to one side or the other of the 

 canals, but few of the many tubules that run directly out- 

 ward from the canals to the external surface being even 

 indicated. Fig. 7 shows the exact number and position 

 of the pores and tubules in a part of the suboi-bital canal 

 where they are particularly numerous, and this, with the 

 general drawings, will give a sufficiently good idea of their 

 arrangement elsewhere. 



The methods employed in these dissections were, to 

 examine the undissected head by slanting lamplight, which 

 brought out the pores ; to scrape off first the delicate 



