THE GENITAL SYSTEM OF THE MYXINOIDEA: A STUDY 



BASED ON NOTES AND DRAWINGS OF THESE ORGANS 



IN BDELLOSTOMA MADE BY BASHFORD DEAN 



By J. LeRoy Conel 



Professor of Anatomy 

 Boston University School of Medicine 



INTRODUCTION 



The Myxinoids, or slime eels, have been the subject of a considerable amount of 

 inquiry and discussion by many investigators in Europe and America. The interest of 

 investigators has been challenged by these eels because they are the lowest living verte' 

 brates. Some of the earliest authors believed that the Myxinoids practice parasitic or 

 semiparasitic habits of Hving on the bodies of fishes, therefore much controversy has 

 arisen as to whether these animals are primitive or degenerate, and whether they should 

 be classified as Gnathostomata or Agnathostomata. The excretory system has been 

 characterized by some writers as a pronephros, by others as a pronephros in the early 

 stages of development but later becoming transformed into a mesonephros except at the 

 anterior end, and by others as a very small anterior pronephros and a posterior segmental 

 mesonephros which develops in the usual manner. The homologies of the different parts 

 of the brain, also, have been variously interpreted. 



The genital system in particular has been extensively investigated, with considerable 

 difference of opinion both as to facts and interpretation. Because of peculiarities in the 

 structure of the genital organ, the Myxinoids were believed by some of the early in^ 

 vestigators to be hermaphrodites, and this opinion continues to be incorporated in modern 

 text-books. The egg and its membranes have received much attention, resulting in a 

 variety of interpretations, and the time when the eggs are spawned has long been a matter 

 of speculation. 



For many years the assistance of embryology in solving these and other problems was 

 denied because no one was able either to find the embryos developing in the natural en- 

 vironment or to obtain them by keeping the eels in captivity. Neither could paleontology 

 contribute toward the elucidation of any of the many obscure problems, for until very 

 recently no fossil of a myxinoid has been found with the single exception of Palaeospondy- 

 lus, supposed by some to be a Devonian lamprey, but this is denied by Dr. Bashford Dean. 



Many important contributions toward a solution of some of the problems regarding 

 the Myxinoidea were made by Doctor Dean while he was Professor of Zoology in Colum- 

 bia University. Many of the observations which he made during his investigations at 

 that time, however, have never been published. Doctor Dean spent the summer and fall 

 of 1896 in searching for the embryos of Bdellostoma stouti in Monterey Bay at Pacific 

 Grove, California. He succeeded in collecting the first fairly complete series of myxinoid 



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