"376 PROCEEDINGS OF THE ACADEMY OF [May, 



experimental work was done at the Marine Biological Laboratory at 

 Woods Hole from June 7 to September 20, 1910. 



In regard to the methods for preparing sections, after the legs had 

 been removed from the spiders, they were cut into short pieces and 

 then were fixed a few hours in either strong Flemming's solution or 

 in Carnoy's fluid, the latter being the modified form of equal parts of 

 absolute alcohol, glacial acetic acid and chloroform with corrosive 

 sublimate to excess. Carnoy's fluid was the better of the two fixatives 

 and my best sections were obtained by leaving the material in the 

 fluid over night. The material was dehydrated in the ordinary way 

 in alcohols but was cleared by using the sinking method in cedar oil. 

 It was embedded about an hour in hard paraffin (54° C.) On account 

 of the hard cuticula perfect serial sections were impossible, although 

 good sections were had in two ways: (1) After fixation the material 

 was left in a solution of equal parts of 70 per cent, alcohol and glycerin 

 two oi' three weeks; (2) The material was fixed immediately after 

 moulting. The latter method was the better one for the cuticula was 

 very soft and thin. The sections were cut ten microns thick and were 

 stained with Uelafield's hsematoxylin and eosin. 



In preparing the external surfaces for the study of the disposition 

 •of the lyriform organs the following method was pursued: A large 

 slit was made on the dorsal side of the abdomen of the specimens, 

 then they were dropped into a cold solution of caustic potash. In 

 this solution the adults remained from six to thirty-six hours, the 

 time depending on the size of the individual; for the spiderlings one 

 hour was sufficient time. After being removed from the caustic 

 potash solution all the internal disintegrated tissues were carefully 

 removed with a camel's hair brush and water. Now the "skins" 

 were permanently mounted between two cover slides in a one-fifth 

 saturated solution of potassium acetate. Such a solution gave the 

 proper refractive index so that the slits appeared more or less trans- 

 parent while the surrounding cuticula was usually darker. The two 

 cover slides were held together with a solution of asphaltum. For 

 the dark colored specimens bright day light was used, but for the 

 .light colored ones a strong yellow artificial light was the only one 

 which was satisfactory. 



A. The Lyriform Organs. 



il. MORPHOLOGY. 



1. Structure of Lyriform Organs. 



A lyriform organ is a eutieular structure peculiar to arachnids, 

 ^composed usually of several single slits which lie side by side and 



