KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 



33 



capsule would be thrown beyond its confines completely at the time of explosion, 

 which does not seem to be the case in any of Chatton's figures. On the con- 

 traiy, the extreme posterior end of the filament remains connected with the 

 extreme anterior end of the nematocyst in all cases (fig. G, 10), a fact that 

 would point to an intimate relation between the two structures. It seems prob- 

 able, therefore, that the filament in the nematocysts of the dinoflagellates has a 

 tubelike structure and is everted at the time of discharge of the nematocyst, 

 as in the case of the Cnidosporidia and Coelenterata (figs. H, 4, 5), 



.' 4 



Fig. G. Development of the nematocysts of Polykrikos. After Chatton (1914c, pi. 9, figs. 2, 4-7, 10-12, 

 text figs. 6, 7). 1. Mature nematocyst with its cnidoplaste attached. 2. Cnidoplaste detached with differen- 

 tiation beginning at anterior end. 3. Cnidoplaste with the introvert and stylet developing. 4. Body of cnido- 

 plaste dissolving, leaving vacuole around it. 5. Further stage of the same, changing of cnidoplaste into 

 cnidogene. 6. Cnidogene stage, introvert and flagellum suspended in vacuole, sphere forming anteriorly which 

 is future cnidoplaste. 7. Further development of cnidogene. Body of nematocyst forming in vacuole. 8. 

 Cnidogene developed into young nematocyst. 9. Further development of the same. 10. Exploded nematocyst 

 with stylet thrown off. X ? 



Chatton figures cases in wliich the nematocysts have been caught, as it were, 

 in the act of exploding, with the filament partly within and partly without the 

 capsule. This appearance is not inconsistent with our explanation of the pro- 

 cess as that of an eversion of a slender tulje, as may be seen by partly with- 

 drawing the finger of a glove that has Ijeen turned inward. A point will be 

 reached where the finger extends some distance on each side of its point of 

 insertion, as does the filament in his figures (1914c). 



