22 ON THE ANATOMY OF THE FAMILY OF THE MEDUSA 



surface was turned towards the eye, the openings of the sacs could be 

 perceived : the sacs were filled with spermatozoa with triangular heads, 

 about lovoo-th of an inch in diameter, and very long, fine, delicate 

 tails, fig. 3 1 a. The course of their development appeared to be as in 

 Phacellophora. 



50. Rhisostojiia^LnA Phacellophora then agree in having the sperma- 

 tozoa developed in sacs connected with the inner " foundation mem- 

 brane " and opening internally. It would appear from this that the 

 exit for the spermatozoa is through the mouth of the animals, though 

 this course in Rhizostouia would certainly be a rather circuitous one. 



51. The individual of Cephea (C. ocellatd) which I examined 

 resembled, with regard to the generative organs, a young Rhisostoma. 

 The line of generative tentacles was present, but the generative organs 

 were undeveloped. According to Will, the structure of the testis in 

 Cephea Wagneri closely resembles that of Rhisostoma. He says that 

 there is a cavity under the disc into which the canals of the arms and 

 disc open ; that the floor of this cavity is formed by a thin membrane 

 covered with fine tentacular appendages, and that the band-like testes 

 are attached to the under free surface of the membrane ; they consist 

 of pyriform sacs {flaschcnfonnigen Driischeii) closely applied together, 

 and each opening independently below. The spermatozoa are elon- 

 gated and cylindrical, and have a very long, fine appendage. 



52. With regard to the imisctilar system of the Medusae, such 

 observations as I have made lead me to believe that the muscular 

 fibres are always developed in the outer "foundation membrane." In 

 Rhizostoma the muscular fibres of the under surface of the disc are 

 flat, pale, and from tbVu th to ^Jo^h of an inch in diameter. They run 

 parallel to one another, but the lines of separation between them are 



not continuous throughout, but thus : each fibre is . 



made up of very small and indistinct fibrils, which "" 



are transversely striated, the striation being most 



distinct at the edge of the fibres. . ~ " 



53. I have not observed any indubitable trace of a nervous system 

 in the Medusae. 



54. Will has described a blood-vascular system, consisting of a 

 system of canals inclosing the water canals and containing a distinct 

 fluid with cells floating in it. I have paid particular attention to this 

 point in all my examinations of , the Medusa;, but notwithstanding 

 that I have had species of the very same genera {Cydippe, Cephea, 

 Thaiimantias) under my hands, I have never observed any trace of it. 

 I am at a loss even to understand what he means, unless, as I strongly 

 suspect, he has taken the outer foundation membrane, which occa- 



