34 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Another point somewhat unconvincing in Chatton's work is the role he has 

 attributed to the stj^let. This he figures as a slender rod, slightly conical, with 

 the base wider than the apex (fig. G). This shape is constant in all his figures 

 showing the stylet in the still uuexploded nematocyst. After the explosion 

 has taken place its position in the center of the thickened portion of the introvert 

 is occupied by the filament. Near at hand, as though pushed out of position 

 by the filament, is a rod (fig. Cr, 10) differing in length and thickness from the 

 stylets which he has figured in the uuexploded nematocysts. In our oavu 

 material (fig. F) the base of the filament after it has been discharged shows a 

 slight enlargement comparable with the appearance of the stylet in the uuex- 

 ploded capsule. It seems probable, therefore, that here, as in the nematocysts 

 of the eoelenterates, the stylet functions as the base of the extruded filament. 



Tlie development of these interesting organelles has also proved to be a 

 puzzling question, the solution of which has been greatly advanced by the re- 

 searches of Chatton (1914c). Faure-Fremiet (1913) has offered a scheme of 

 development of the nematocysts from the small refractive granules conunon 

 in the cytoplasm. He presents no stages, however, between the small roimd 

 eranules and the elongate bodv of the voung nematocvst. These refractive 

 granules and small globules are common throughout the dinoflagellates gener- 

 ally, and since nematocysts are not common elsewhere more evidence is required 

 before they can be considered jiart of the development of these peculiar organs. 



Chatton (1914c) offers another type of development which is cyclical in 

 character and of a consideral^le degree of complexity (fig. G). It consists of 

 three distinct stages, the first of which is the "cnidoplaste" (figs. G, 1-5), which 

 appears to arise from an organ resembling the centrosome. The cnidoplast 

 arises by a process of "autogenese" from the mature uematocyst. Part of this 

 process is shown in figures G, 6, 7, iu the body forming at the anterior end of 

 the developing nematocyst. The cnidoplast is not enclosed in a chitinous cap- 

 sule and deliquesces readily in sea water. It goes through a process of devel- 

 opment by which the anterior end is transformed into a new structure, the 

 "enidogene," and the remainder of the body dissolves, its place being occupied 

 by a large vacuole (figs. G, 2-6). The enidogene gradually develops into the 

 finished nematocyst. Chitinization of the body of the future nematocyst or 

 cnidoeyst takes place in this vacuole while further development of the internal 

 structure of the capsule progresses (figs. G, 7-9). This results in the pro- 

 duction of the filament and the introvert or ampulla, and the enidogene becomes 

 the mature nematocyst (fig. G, 9). 



The mmiber of mature nematocysts in the l)ody of both Polijkrikos and 

 Nematodinium varies in different individuals. In our own material of 

 PolijkHkos the number has run from one or two less than the number of zooids 

 to twice the number of zooids of the body. Chatton has found that variations 

 may exist in the number of young forms or "cnidoplastes" (fig. G, 2), and 

 also in the number of mature nematocysts. In the secondary stage of their 



