OBSP:ilVATl()NS ON THE DEVELOPMENT ANT) ^[TGKA- 

 TION OF THE URTIOATING OllGANS OF SEA NETTLES, 



CNIDAlilxV. 



By Louis Murbach, Pit. D. 



Visitors to the seasliorelmve frequently liad opportiiuity for becom- 

 ing more or less acquainted with Sea Anemones, Jelly-Fishos, or even 

 the large Portuguese Man-of-War, and other Siphonophora. 



If the arms (tentacles) of the former, or the long capturing tilameut& 

 of the latter, have been touclied, inadvertently or through a morecare^ 

 ful examination, a burning stinging sensation was experienced where 

 the tentacles came into contact with the more delicate skm of the 

 hands or other parts of the l)ody. 



These animals not only can nuike it unpleasant for their enemies, but 

 by the same means can also overcome their prey. The ability to exer- 

 cise this offensive and defensive warfare is due to the possession of very 

 minute weapons called nettling organs. The observer has now become 

 familiar with a most important function in the economy of these ani- 

 mals— that of nettling— which serves both as a means for gaining their 

 livelihood and for their protection. 



It is a suitable recognition of this power, that those groups of the 

 Ccelenterata possessing it have been called Cnidaria. 



The nettling organs can be studied satisfiictorily only with the micro- 

 scope, as they are single celled organs and consequently very minute. 

 They are situated in the outer cell layer, the ectoderm of the tenta- 

 cles or on special filaments- the acontia of the Actinia' in the gastric 

 cavity— the pertinent tissues of which are derived from^i e ectoderm.-^ 



^rniis paptTr is to constitute a brief report of those results, obtaiued .Inrino- ,ny 

 ocenpancy of the ftniithsonian table at the Naples Zoological Station, which it was 

 thought would prove of interest to Ihe public. The table was occupied from April 

 25to''.Inne 25, 1894. 



n believe it is still generally hvU that the nettling organs ot the mesentcnal 

 filaments of the Jcthnw are of en.h.dernnc origin. But at the time this work was 

 done I came acrosp a paper of Boveri's (Uober Eutwickclung und Verwaud- 

 s.haftsbeziehungen der Actinien; Zeit. f. wiss. Zool., XLIX, Pt. 3, 1890) conhrming 

 the view formerly held by Heider (Ein Beitrag zuv Anatomic der Actin.eu ; Sitz bcr 

 d Acad d Wiss., Wien; LXXIX, 1879) that the mesenterial filaments are of 

 ectodermic origin, being derived from the lining of the gullet. This would place 

 the ori-in of the nettling organs of all Cnidaria from the ectoderm. I can not t.nd 

 that this application has l)efore been made, yet it can not, I should suppose, so long 

 have been overlooked. 



riDccedings of the Uiiiti-il Slati-s Naliuual Museum, Vol. XVIII— Xo. lO'.lT. ^^ ^ 



