1873.] 159 [Putnam. 



eggs are one inch in length, and one-half an inch in width, and the 

 anchor-shaped hooks, of which there are about eighty at each end, 

 are about one-tenth of an inch in length. At about one -fifth of an 

 inch from one end of the egg case is a slight lip or groove round the 

 case, into which the substance of the egg itself projects, so that on 

 taking the egg from the case, a corresponding ridge is seen round its 

 surface. The egg case is of a beautiful red color, quite tough, and of 

 about the thickness of good writing paper; over its surface are a large 

 number of minute granulations, which are made by projections of 

 points of the shell leaving corresponding pits on its inner surface. 

 On holding the empty case to a strong light and looking with a lens 

 from the inner side, the base of the hooks can be seen to be arranged 

 in four irregular rows round each end, and each hook has its base in 

 a small depression from the outer surface. 



That all this complicated development of the egg and its mem- 

 branes, and the formation of the horny case, with its granulations 

 and projecting hooks, should take place in the delicate and thin 

 membranous sac forming the ovary, and without the slightest trace 

 of any glandular structure, is most remarkable, when we remember 

 the complicated system of glands that is required to bring about the 

 same structure in the development of the membranes of the egg and 

 its case in the oviparous sharks and skates. This is still more in- 

 structive if we recall the fact that the next higher form of fishes 

 above the Myxinoids are the Lampreys, in which the eggs are small, 

 thousands in number, and laid without being protected by cases. 



We thus have in the Myxinoids, the lowest form but one of all 

 Vertebrates, a peculiar character in the formation of an egg case, 

 and in the small number of eggs developed at one time, which is lost 

 in the very next family above it to reappear, under a different mode 

 of development, in the Selachians, a group in every respect struct- 

 urally far above the Cyclostomes. 



In regard to the use of the hooks on the cases of the eggs of Myxi- 

 noids,! believe that they are not so much for the purpose of attaching 

 the eggs after they have been excluded, as they are for holding the 

 egcs together in a chain when dropped from the ovary into the ab- 

 dominal cavity, and thus aiding in their exclusion; as it must be 

 impossible for the eggs to be loose in the abdominal cavity without 

 being united by their hooks ; for, on gently floating two eggs together, 

 their hooks united immediately with such tenacity as to render it 

 almost impossible to separate them without destroying some of the 



