30 



MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



These orgaBelles were first figured by Biitsclili (1873) as " Nesselkapseln, " 

 a term also used by Bergh (1881) in describing the same structures in Pohj- 

 krikos aiiricidaria (P. sch irartzi). Pouchet (1887) figured them as nematocysts 

 without, however, giving the details of their structure, as both Biitsclili and 

 Bei'gli had done. Faure-Fremiet (1913ft, h) was the first one to attempt a more 

 critical analysis of the origin and natiire of these peculiar organelles. He was 

 followed by Chatton (1914c), who figured an elaborate stage of cyclical devel- 

 opment, markedly different from that outlined by Faure-Fremiet. A further 

 analysis of these schemes of development will be given after the minute structure 

 of these organelles has been described. 



long, fl 



Fig. F. PolyTcrikos Biitschli, and its nematocysts. 1. F. l-ofoidi (Kofoid). X 500. Individual of four 

 zoolds. After Kofoid (1907). 2. Nematocyst. X 1550. 3. Exploded nematocyst. X 1148. 4. P. schwart-i 

 Biitschli. X 500. Abbreviations: ant. p., anterior pore; cap., head of nematocyst; epi., epicone; fil, filament; 

 gir., girdle; hyp., hypooone; loiiff. fl., longitudinal flagella; «., nuclei; post, p., posterior pore; sty., stylet; sulc, 

 sulcus; tr. fl., transverse flagella. 



The structure of the nematocysts of both Pohjkrikos and Xemafodiuium 

 is practically identical. The matured organ is found lying naked in the 

 plasma (pi. 11, fig. 122), without any special plasmatic membrane or structure 

 surrounding it, or any differentiated protoplasmic nidus in which it originates, 

 or any external plasmatic structure which might function as a cnidocil. The 

 position of the nematocysts in the body of the dinoflagellate is not constant. 

 They may be found in all parts, though perhaps most frequently in the right 

 half of the body. Their orientation is also subject to great variations, with no 

 apparent relation to the surface of the body. Chatton (1914c) found that the 

 greater number were oriented with the pole of devagination turned towards 

 the surface of the body. In our own material this orientation seems no more 



