﻿OF THE ACALEPH.E OF NORTH AMERICA. 295 



forth here ? And would it not be equally natural to extend similar comparisons to the 

 larger eye-specks of Tiaropsis, and to view the small dark dots at the base of their ten- 

 tacles as corresponding to the loose ocelli scattered more irregularly in spiders and other 

 insects ? 



The position of the ovaries and spermaries (Plate VI. Fig. 3, 4, 5, 9, and 10) seems at 

 first entirely different from that which exists in either Hippocrene or Sarsia. In those two 

 genera the eggs and spermatic cells are developed, (as mentioned above,) upon the whole 

 surface of the central digestive cavity. But in Tiaropsis they form four isolated bunches, 

 placed upon the lower surface of the gelatinous disk, about midway between its central part 

 and its margin, following, however, the radiating chymiferous tubes, to the external surface 

 of which they are attached. This connection of the ovaries and spermaries with the radiat- 

 ing chymiferous system in Tiaropsis is certainly the same, morphologically, as in Sarsia 

 and Hippocrene ; though in the two latter genera the eggs and spermatic cells seem to be 

 connected only with the outer walls of the central digestive cavity. However, if the ar- 

 rangement of the ovaries in Hippocrene be examined very carefully, and their connection 

 with the prominent angles and lateral surfaces of the central cavity be not lost sight of, it 

 will indeed be seen that the development of the bunches of eggs corresponds strictly 

 to the prominent angles of the central cavity, from which the radiating tubes arise, and 

 which the eggs, in their development, follow to some extent before they are laid, as may 

 be seen from Plate II. Fig. 23. Thus the whole difference between the sexual system 

 of Tiaropsis and Hippocrene consists in the circumstance that the four angular bunch- 

 es of ovaries, or spermaries, characteristic of Hippocrene, are somewhat displaced from 

 the centre, and moved halfway towards the edge of the disk, to form the characteristic 

 isolated ovaries and spermaries of Tiaropsis. Organically speaking, however, this differ- 

 ence is so trifling, that I should not be willing upon this basis to establish distinct families, 

 as Professor Forbes has done ; for morphology teaches us here, that there is no more dif- 

 ference in the position of the ovaries and spermaries in Tiaropsis and Hippocrene, than 

 there is between the connection of petiolate and decurrent leaves with the stem to 

 which they are attached. 



At various periods during spring these organs appear very differently, being at first 

 scarcely distinguishable as a slight ribbon-like swelling along the middle track of the 

 radiating tubes. Later and later, as the ovarian and spermatic cells are more and more 

 developed, they form a larger and larger fusiform body, swelling finally into prominent 

 granulated bunches, varying in color in different specimens, from which at last the eggs are 

 hatched. The state of development of the eggs, when they are cast, is rather advanced; 

 for the germs are then ready to escape, or are indeed actually freed from the eggs, before 



