MONOGRAPH OF THK EXISTING CRINOIDS. 367 



All the egg^s, the small as well as the large, are in contact with the rece-ptaculum 

 seminis through a small opening, by means of which the spermatozoa are able to 

 reach them. 



In the mature ovary the ripe eggs occupy the major portion. In size they are 

 about the same as those of Antedon adriatica or A. mediterranea, being 0.3 mm. 

 in diameter; but an accurate statement of their size is difficult to give, for as a 

 result of pressure on all sides they are usually oval or irregular in shape. 



The eggs are inclosed in a thin membrane and enveloped in a follicular epi- 

 thelium with a small opening on the spot where it adjoins the receptaculum 

 seminis. Andersson believes that the cells of this follicle arise from the con- 

 nective tissue cells immediately adjacent to the egg. 



In strong contrast to most comatulids, in which a large number of eggs are 

 matured at one time and extruded simultaneously, the ovary of Isonietra vivipara 

 never contains more than a few mature eggs, with others in all stages of 

 development. 



As the eggs become ripe they are fertilized and extruded one by one into the 

 marsupium. Thus the marsupium contains most commonly three, and never 

 more than five, embryos in different stages of development. Entry into the mar- 

 supium appears to be by means of slits torn in the wall by the pressure of the egg. 



In confirmation of Andersson, Mortensen states that the fertilization probably 

 occurs within the ovary. He did not succeed in finding any fertilized eggs still 

 lying within the ovary, but, on the other hand, he found no unfertilized eggs 

 within the marsupium. 



GENITAL ORGANS OF NOTOCKINUS VIRILIS. 



Figs. 1349-1352, pi. 55. 



In Notocrinus virilis^ as described by Dr. Th. Mortensen, the genital organs 

 lie almost wholly on the arms. 



The testes are enormously developed, forming two alternating rows of con- 

 spicuous white bodies, closely appressed along the median line of the arm, which 

 appears considerably swelled. They are about 4 mm. long and look like small 

 beans. 



On their distal side, in the angle between the pinnule and the arm, there is a 

 small pore, through which the spermatozoa escape. 



The testes occur from P3 to Pj,. 



Mortensen suggests that the large size of the testes may be accounted for by 

 the fact that the spermatozoa have to find their way to the eggs in the marsupium 

 through its small opening, which involves considerable difficulty. 



The ovaries, which are much smaller than the testes, about 2 mm. in length, are 

 similarly situated on the arms at the bases of the pinnules, but are not in contact 

 along the median line. They occur from P3 to about P,,. or a little farther out in 

 very large specimens. As in the case of the testes, there is no definite outer limit, 

 they merely diminishing gradually in size to the twelfth or fourteenth brachials, 

 beyond which point they may be continued in rudimentary form. They are 

 generally slightly concave distally, where they abut upon the marsupium. 



