No. 2.] MORPHOLOGY OF THE MYXINOIDEI. 189 



partial dissections of Myxine and Petromyzon, and the results 

 which we conjointly publish are vouched for alike by both of 

 us. Mr. Jackson has made a complete, extremely careful, and 

 independent study of the myxinoid skeleton, and Dr. Ayers 

 has likewise restudied the musculature. We have checked 

 each other's work on the skeleton, and while we do not pre- 

 sume to have exhausted the subject, we think we have not 

 overlooked any very important anatomical details. The follow- 

 ing papers on myxinoid anatomy are now ready for the press : 



"On the Morphology of the Eye of Bdellostoma dombeyi." 



"Ovigenesis in Myxinoids." 



" On the Structure of the Slime Glands and Skin of Bdel- 

 lostoma dombeyi." 



Preservation of Material. 



The Bdellostoma material used in the present investigation 

 was killed and hardened in lo/o formalin, and preserved partly 

 in alcohol and partly in formalin, as well as in the following 

 mixture of the two : 95/0 alcohol, 6 parts ; 2/0 formalin, 4 parts. 

 The formalin has been found to be exceedingly valuable in 

 preserving specimens for study of the cartilaginous skeleton. 

 The effect of formalin is to give the cartilage a pink or reddish 

 tinge, which gives an excellent differentiation and brings out 

 many points of structural detail which might be overlooked 

 in alcoholic material. Occasionally, however, non-cartilaginous 

 connective tissue takes on the same tinge, so that in all doubt- 

 ful cases a histological examination is necessary. In all other 

 respects as well, the formalin material is far superior to 

 alcoholic material. 



The Skeleton of Bdellostoma. 



The skeleton includes all those condensations of the meso- 

 derm which are specially developed to support or protect the 

 softer tissues of the body. The skeletal parts which are within 

 the body make up the endoskeleton, while those in the external 

 integument constitute the exoskeleton. In the latter case the 

 mesoderm enters into intimate relations to ectodermic structures. 



