Structure of Meigehna.. 427 



projected from the edge of the snout in a specimen apparently 

 undergoing repair after injury*. 



II. The Muscular System. 



Head. — The muscular system of the snout consists of a 

 median and a lateral pair of longifudinal muscles. 



The median form symmetrical muscles which stretch from 

 the tip of the snout (in advance of the lateral) to the mouth. 

 Viewed from above the fibres slant backward and inward 

 toAvard the middle line throughout the greater part of the 

 muscles ; but after they separate posteriorly the direction of 

 the fibres is more nearly transverse — slanting from above 

 downward and inward at a wide angle and as a boldly 

 marked series. If a transverse section be made at the very 

 tip of the snout, the area is hypodermic and cnticular, with 

 the exception of two small oval regions representing the 

 attachments of these muscles, which are widely separated by 

 a hypodermic wedge. The latter gradually diminishes, so 

 that by-and-by the section of the central muscles has the 

 aspect of a pair of spectacles, the muscles forming the eyes 

 and the nasal bridge being represented by the chitinous 

 connecting-bar, Mhich is continuous with the investment of 

 each muscle. 



As the chitinous basement-tissue just mentioned is of 

 considerable functional importance in the snout, it may be 

 well to describe its arrangement before proceeding further 

 with the muscles with which it is intimately associated. As 

 indicated, the chitinous supports in this region of the snout 

 form for each muscle a complete investment, which, more- 

 over, is connected with its fellow by a median bar ; while 

 from the outer edge of the chitinous rim a thin lamella passes 

 outward to the tip of the hypodermic expansion, and there- 

 fore represents the claspers or limbs of the spectacles (in 

 transverse section). By-and-by (proceeding backward) a 



* lu these days of elaborate instrumental aids it is well to mention 

 that, though the majority of such appliances were at command, nothing 

 better has been found than the following simple method of examining 

 the structure of such forms in the prepared state : — The specimens are 

 placed in absolute alcohol, fitted to very fine corks, again immersed with 

 the latter in alcohol, cut in the hnnd with a keen razor, and mounted in 

 chloride of calcium. Dexterity will not, as a rule, enable the observer to 

 make trustworthy researches on badly prepared examples of the Annelida. 

 If the tissues are so soft that the pressure of the thin glass cover injures 

 them, it is sometimes convenient to mount them with a very fine section 

 of the cork in a suitable position. 



