MATTHAI— RECENT COLONIAL ASTR^ID^ 15 



axial strand merges may be the residue of the chromatin left after the former has grown 

 to its full length. Type III, like II, would then be a complete cell. 



If the above study of the nematocysts be confirmed by living material, then the 

 trumpet-shaped body (a modified nucleus) of I would be comparable only with the axis 

 of II and with the thread of III, its wall and filament ""' being homologous respectively 

 with the sheath and spiral of the last two types, but without a chromatic central 

 core. 



Of the four kinds of nematocysts described and figured by Gosse (53, PI. 11), the 

 " spiral cnidse (cnidae cochleatse)," which are confined to the walls of the tentacles and 

 whose thread (" ecthorseum ") is without any armature, is in all probability the same 

 as type I, the " chambered cnidse (cnidae cameratse) " and " the tangled cnidse (cnidse 

 glomiferge) " come near type III, the latter having no "barbed bristles" ("pterygia") 

 on the spiral ("strebla") surrounding their thread, while the " globate cnidse (cnidse 

 globatae) " may be glandular structures and not nematocysts. 



Previous authors who have made the study of nematocysts agree that they arise 

 in interstitial cells of the epithelium. At first a vacuole is formed in the cytoplasm 

 of such a cell which becomes the capsule of the nematocyst. Opinion is divided as 

 to the nature and mode of development of the filament. Of the many views that have 

 been put forward the two main ones are (a) that the filament is formed inside the capsule 

 (Bedot, 4), (b) that it develops outside the capsule, becoming subsequently invaginated 

 into the latter (Jickeli, 73; Nussbaum, 107; Murbach, 106). Iwanzoff (72), on the other 

 hand, holds an intermediate position that the filament is at first partially invaginated by 

 its distal end, the invagination becoming complete with the full development of the 

 nematocyst. According to these authors the filament is a cytoplasmic product, the 

 nucleus of the nematocyst persisting outside the capsule. 



In the last two types I have not been able to make out a neuro-muscular process as 

 in I, and in none have I observed any process suggestive of a cnidocil. 



After completing the above studies of the nematocysts my attention was drawn to 

 a paper by Theodor Morofi" (" Entwicklung der Nesselzellen bei Anemonia," Archiv 

 Zellforsch. iv. p. 142, 1909), in which the author has traced the origin of the filament to 

 nuclear elements. Moroff has described two kinds of nematocysts from the tentacles 

 of " Anemonia sulcata," (a) " spirocytes," which are similar in appearance to type I, and 

 (b) " nematocytes " which resemble type III. As far as I have been able to understand 

 his description, each of these has a double wall (in transverse sections of my types 

 the walls consist, in every case, of a single membrane), the outer " sklera " being 

 cytoplasmic in origin, while the inner "propria" is chromatic and continuous with the 

 thread which is also formed by the union of chromidia ; he regards the axis of the 

 " nematocytes " (fig. M) as continuous with and having the same origin as the thread and 

 capable of being everted. The nuclei as they become modified into the nematocysts 

 wander from the base of the ectoderm to its periphery. 



* I have applied the term "filament" to the structure in type I, while the use of the term "thread" 

 is restricted to the complex structure in type III, which consists of an axial strand surrounded by a 

 sheath and by a fine spiral. 



