738 UBTICATIXG ORGANS OF SEA NETTLES— MURBACH. vol.xviii. 



used-up batteries and euds of the filaments, were replaced by the 

 extensive growth (Xachschub) of the latter. 



In Velella, Bedot/ later found canals filled with nettling organs 

 extending from the great mass of developing nomatocysts, under the 

 so-called liver, to the outer layer of cells on the under side of the animal. 

 But he did not consider the question of the manner of their transpo- 

 sition. 



In Hydra, I^ussbaum^ believed that the movement of nettling organs, 

 along the tentacles, was facilitated by the slightly twisted condition of 

 the latter. 



The reasons for my conclusion, previously stated, that the nettling 

 organs lu'opel themselves from place to place (excepting in the Siphon- 

 ophora), were that I also found the cauals which Bedot had seen in 

 Velella; ^ but more than this, I found that the uettliug organs are always 

 turned with the basal, i. e., with the larger mass of protoplasm and 

 nucleus, in the direction of motion, while the discharge pole points to the 

 rear. Furthermore, that the fixed cell-body shows the amcjeboid form. 

 Finally, that in many Hydroids one can frequently observe nettling 

 organs lying parallel to the surface of the tentacles, their orientation 

 as before described, showing that they are proceeding upward on the 

 latter. This was further confirmed by the more careful drawings of 

 two of the works consulted, one by F. E. Schulze^ and the other by O. 

 and E. Hertwig. ^ 



Statement of results. — Xow the ohscrrations of living material bring 

 the most conclusive proof. From specimens of Velella to be examined, 

 small pieces containing nettling organs were teased a little and lightly 

 flattened under the cover glass. Manj- nettling organs showed amoe- 

 boid changes of form. The movements were slow but definite. One 

 case, hoAvever, which was observed for fifteen minutes, made such pro- 

 nounced and rapid amoeboid movements, that it might well have been 

 taken for an A^naha, which had swallowed a nematocyst. 



As Pennaria caroUnii was easily obtainable, it was used as a repre- 

 sentative of the Hydromedusaj. At first a.hydranth was teased and 

 placed with some sea water under a cover glass. The protoplasm ofi 

 the nettling cells was in many cases passing through changes of form, 

 but no definite locomotion was observable. In order not to mistake 

 any rotation of the nettling organ for change of form, in this and all 

 subsequent cases, the si^ines in the base of the thread were carefully 

 observed simultaneously with the contours of the cell-body. For other 



' Eecherches sur I'orgau central et le sytseme vasculaire cle Velelles; Recueil zool. 

 Suisse, I, 1884. 



-Ueber die Theilbarkeit d. leb. Materie, II; Archiv f. Micros. Anat., XXVII, 

 1887. 



* According to bis preliminary report (Zool. Auzeig., No. 461) Scbneider bas 

 observed tbe same for Forpita. 



■•Ueber den Ban und die Entwickelung von Syncoryne Sarsii, 1873. 



^Daa Nervensystem und die Sinuesorgane der Medusen, 1878. PI. V; fig. 26. 



