ii THE VOYAGE OF H.M.S. CHALLENGER. 



Unfortunately, however, the fragments of the only specimens which I obtained of these 

 two beautiful Medusae, proved on closer examination to be so imperfect and so badly pre- 

 served, that I was obliged to give up all idea of their further description and illustration. 

 On the other hand, I gained a special advantage in the description of a few other deep- 

 sea Medusae, whose single specimens from the Challenger collection were also insufficiently 

 preserved, as I was able to complete it by means of material procured elsewhere. 

 I have to thank Professor Steenstrup and Dr. Lutken for several well-preserved specimens 

 of Ptychogena pinnvXata and Pectyllis arctica from the Zoological Museum of Copen- 

 hagen, and my friend Mr. Gregor Buccich for several excellent specimens of Drymonema 

 victoria from the island of Lesina in Dalmatia. Three species, of each of which the Chal- 

 lenger collection only contained an imperfect fragment, I took myself living with the 

 tow-net, and thus had an opportunity of examining them minutely ; Pectanthis aster- 

 oides from the Mediterranean, Cunarcha ceginoides from Lanzarote, one of the Canary 

 Islands, and Polycolpa forskalii from the Red Sea. Of the majority of the twelve other 

 species I had, unfortunately, only a single specimen at my disposal, and that was often 

 imperfect; still I hope that, with the assistance of the comparative morphology of the 

 most closely allied Medusae, I have satisfactorily reconstructed their organisation. 



It is by no means certain that all the eighteen deep-sea Medusae described below are 

 constant inhabitants of the deep sea ; the method of capture by the tow-net by which 

 such delicate and fragile organisms are often brought from great depths of the sea is still 

 imperfect, and it is probable that the greater number of Medusae brought up apparently 

 from the greater depths, really swim in shallower water and are only taken in " hauling 

 in " the net. Those Medusae, on the other hand, may be regarded with greater proba- 

 bility as permanent and characteristic inhabitants of the deep sea, which have either 

 adapted themselves by special modifications of organisation to such a mode of life, or which 

 give evidence by then- primitive structure of a remote phylogenetic origin. As such I 

 consider of the nine Craspedotae described, — first of all the three Pectyllidae (Pectyllis, 

 Pedis, and Pectanthis), and secondly Cunarcha and jEginura; among the nine Acra- 

 spedae, Tesserantha, the two large Periphyllidae (Periphylla and Periphema), and the 

 two remarkable Ephyridae (Nauphanta and Atolla). It appears, however, from the occa- 

 sional observations of single naturalists, that other Medusae species also (especially 

 Charybdeidae and Pdiizostomidse) inhabit for the most part the bottom of the sea, and 

 pass into considerable depths. We may therefore hope that the following description of 



