3(J0 W. K. BROOKS ON THE LIFE-HISTORY 



octonaria; a Trachomedusa, Liriope scutigi m ; an Anthomedusa, Turritopsis nutricula; 

 and a Leptomedusa, Eutima mira. I give detailed accounts of these four life-histories, 



as I believe that in each case I have enough new facts to warrant their publication as 

 purely descriptive work, independently of their usefulness as illustrations. 



I take this opportunity to express my indebtedness to Messrs. A. lloen & Co. of 

 Baltimore; who, prompted by their interest in the advancement of science, have warmly 

 seconded my efforts to obtain satisfactory photo-lithographs from pen drawings, and 

 have permitted me to draw at will upon their technical knowledge, and upon the 

 resources of their establishment. 



The four species which I have selected arc among the most abundant and character- 

 istic medusa? of our southern coast, and as no figures of the adult Cunocantha octonaria, 

 or Liriope scutigera have ever been published, and as nothing whatever has ever been 

 known of the life-history of Turritopsis or Eutima, I have made use of the opportu- 

 nities which have been afforded by a residence of several summers on our southern 

 coast to obtain a thorough knowledge of these common species. 



In a recent paper (1), A. Agassiz says that "Ilaeckel's work shows how much pro- 

 gress could be made in our knowledge of Acalephs by selecting a few properly placed 

 stations where Medusa? could be studied advantageously," and I hope that this paper will 

 also serve to exhibit the value of such stations. 



The four species which I have studied have all been accurately described by McCrady 

 (48), but as my daily familiarity with them for several seasons has enabled me to add 

 many new points, and to correct the few errors which occur in his writings, it seems 

 best to preface my account of the development by a brief revision of the systematic 

 zoology of each species. This is the more necessary as an unfortunate accident de- 

 stroyed nearly the whole edition of McCrady 's papers soon after they were printed, and 

 they are now almost unattainable by the student ; and while his descriptions are very 

 graphic, later writers have often given his specific names to other Medusa' than those 

 which he studied. 



Section I. The Narcomedusae. 



Plates 43, 44. 



Although Cunina and its allies have, in times past, been regarded as Discophorae rather 

 than Hydromedusae, chiefly on the account of the fact that the gelatinous substance of 

 the bell is lobed, and also on account of the very striking resemblance between a Cunina 

 and an Ephyra, I think that naturalists are now almost universally disposed to agree 

 that these resemblances are superficial and that the Cuninasand JEginas are true veiled 

 Medusas. The establishment of a correct view of their affinities is due in great part to 

 the careful study of their anatomical structure, which Haeckel was led to undertake on 

 account of his remarkable hypothesis that they are genetically related to the Geryonidae, 

 and that the two forms are stages in the same life-cycle ; and we can well afford to over- 

 look this error since its fortunate result has been a clearer insight into the affinities of 

 the most instructive of all the Hydromedusae. His conclusions regarding their relation- 

 ship to the Craspedotae are so generally received that it is unnecessary to discuss the sub- 



