OF THE HYDROMEDUSJE. 393 



ance, and are fringed by the stalked bunches of large prominent lasso-cells which have 

 been described in the adult by McCrady and others. 



At about this time traces of the reproductive organs made their appearance in the 

 walls of the proboscis at the lower ends of the masses of endoderm cells. The tentacles, 

 at the stage shown in tig. H, arc still carried in two cycles: the interradials being higher 

 than the perradials. There are only eight, and no more were developed in the medusa' 

 which I reared from the hydra, although I captured many specimens in the same state, 

 and at all the following stages up to maturity. 



In specimens from one to two weeks old the lower surface of the very wide velum, 

 fig. O, is pushed ont to form eight hemispherical pouches; four of them radial and four 

 interradial, in the planes of the eight tentacles. They project so much that they are quite 

 easily seen in a profile view, and I have represented them in fig. H. May they not be 

 homologous with the pouches, which, in the ocellate medusae become closed and con- 

 verted into the marginal vesicles? 



The adult medusa is shown in figs. 7", J and K. When it is swimming up from the 

 bottom the tentacles are carried tightly curled up close to the edge of the bell. When it 

 reaches the surface they are suddenly extended on all sides, shown in fig. K. They 

 are nearly straight, but their tips are a little bent and sometimes coiled. This attitude 

 is preserved only for a few seconds and the medusa at once begins to sink towards the 

 bottom, while the tentacles coil up at their tips and assume the position shown in fig. I. 

 The bell also becomes flattened and nearly hemispherical, and before the animal reaches 

 the bottom of the aquarium it usually assumes the appearance which is shown in fig. J. 

 As it nears the bottom it suddenly draws in its tentacles and rises to the surface, and 

 again extends them, as shown in fig. K. 



The plate, which has been photo-lithograohed from sketches and studies which were 

 made from the living animals, may, I believe, be relied upon as a faithful picture of the 

 life-history of Turritopsis, and I trust that this accuracy, which is often lacking in draw- 

 ings which are carefully finished at home, may compensate for the roughness and lack of 

 transparency which are unavoidable in a pen-and-ink sketch. The figures of the adult 

 medusa?, I, J, Iv, are much less magnified than the others, which are all drawn to the 

 same scale. 



Eutima. Plates 38, 39, 40. 



I have selected Eutima as an illustration of the life-history of the second of the four 

 orders, into which Haeckel divides the Craspedota or veiled medusas. This order, the 

 Leptomedus^, includes the Craspedota which are set free as buds from an asexual 

 Campanularian nurse and which have the reproductive organs on the radial canals. Ocelli 

 on the bases of the tentacles are usually absent, and marginal vesicles are almost uni- 

 versally present, and are developed along the veil at its junction with the umbrella, and 

 contain ectodermal otolith cells. 



Haeckel divides the order into four families, in the third of which, the Eucopiixe, or 

 Leptomedusae with marginal vesicles and four simple unbranched radial canals, Eutima 

 is placed, being included in the third of Haeckel's sub-families, the Euttmid^ or 

 Eucopidse with eight adradial marginal vesicles, and with the stomach at the end of a 

 proboscis or peduncle. 



