THE NAUTILUS. 143 



heart (or into the region of the heart) of Chromodoris by means 

 of a syringe and hollow needle. A " Record " syringe, such as 

 is used by surgeons, is useful for this purpose. Within an hour 

 or so depending on the temperature, on the size of the animal, 

 and on the exact amount of the narcotic that has been injected 

 the nudibranch will be fully anaesthetized, usually with the 

 gills and rhinophores fully extended; frequently also the genital 

 papilla will be protruded, and the pharynx everted. It is ad- 

 vantageous to add a few crystals of chloretone to a small vol- 

 ume of sea water containing the nudibranch; furthermore, 

 several injections of the cocaine may sometimes yield a better 

 result than a single dose. 



When completely anaesthetized, the animal may be killed 

 and fixed in 75 per cent, alcohol. Precipitated slime, on the 



surface of the body, can be subsequently removed with a camel's 

 hair brush. In order to avoid the distortion which inevitably 

 results if these large nudibranchs are fixed while they rest upon 

 the bottom of a dish, it is well to suspend them vertically in 

 the fixing fluid until they are killed and begin to harden. This 

 may be done by gripping the caudal extremity of the foot be- 

 tween the jaws of a light "artery clamp" or some similar in- 

 strument; or a thread may be sewn through the foot for this 

 purpose. 



The injection of a relatively small amount of a narcotic 

 usually gives much better results than does the attempt to anaes- 

 thetize these nudibranchs by adding magnesium sulphate, or 

 chloretone, to the seawater containing them. In the latter 

 method, not only does the surface frequently become covered 

 with a number of vesicular blebs, edematous in appearance, but 

 also the proper time for removal to the killing fluid must be 

 selected with considerable care. A similar procedure, involving 

 the injection of chloretone into the body-cavity, has been em- 

 ployed by Pearse 1 with holothurians. 



The proper penetration of the fixative is of course important 

 for the conservation of the internal organs. This result may 

 be assured if a fair volume of the fixative is employed, and if 

 in addition an incision several centimeters long is made along 

 the edge of the mantle (preferably on the left side) previous 

 to immersion in the fixative. 



Frequently it is desirable that the normal integumentary 



1 Pearse, A. S. , 1910. Eine Methode, um Holothurien in ausgedehntem 

 Zustande zu konservieren. Zeits. f. biol. Tech. u. Method., Bd. 2, p. 94-95. 



