2G0 Dr. K. C. Schneider on some 



exarnining the nettle-pad (" Nessclvvulst ") in Carmarina 

 hasiafa, I realized that tiie two thickenings of the epithelium 

 correspond to one another. I was also at first inclined to 

 recognize a supporting tissue in them, as the Hertwigs * and 

 others have done ; but the observation of the living animal 

 taught me that we here have to deal with a centre for the 

 formation of nematocysts. In point of fact the filaments 

 (" Senkfiiden ") in Forskalea and the tentacles in Carina' 

 rina are supplied with cnidoblasts by the pad. In Carnia' 

 rina the elements are not large, but in Forskalea, on the other 

 hand, where the nettle-buds also contain capsules of very 

 considerable size, the whole course of development could be 

 traced with wonderful clearness in their young stages at the 

 seat of formation. I must admit that this is not exactly a 

 very easy task ; nevertheless with regard to the series of 

 consecutive stages, as I shall subsequently figure them, I can 

 affirm with tolerable certainty that it corresponds to the actual 

 course of development. In my paper on Hydra f I supposed 

 the thread to arise by ingrowth of the protoplasm into the 

 cavity of the capsule, and tiiereby took the opposite view to 

 ^ussbaum \ and Jickeli§, who observed a formation of the 

 thread outside the capsule. At the present time, when I too 

 have been able to confirm the mode of formation described by 

 the two authors, I have read with real satisfaction that 

 Bedot II, whose papers I unfortunately omitted to consult 

 before, found a develojimcnt of the threads of the nemato- 

 cysts in Physalia and \'elella which agrees with that which I 

 described for Hydra. The question might easily be asked, 

 Who is right, or is every body right ? 1 am inclined to think 

 that in the case of Hydra I overlooked or misinterpreted 

 something or other — I shall, however, investigate the point 

 afresh — and that Bedot did the same ; for it seems to me to 

 be not very probable that important differences of this kind 

 should occur in the course of the development of the cnido- 

 blasts in animals which are so closely allied. This conclusion 

 is strengthened by the fact that I believe I am entitled to 

 assume that the thread develops outside the capsule in the 

 Aetinians also, as represented by Ad unsia Rondelctii (see 



* 0. and II. IleitAvifT, loc. cit. 



t K. C. Sclmoider, " llistologio von Hydra &c.,'' Arch. mikr. Anat. 

 3,5 I3d. 



X M. Niissbauni, " Ueber die Theilbarkcit dor IcbiMuiiirou Matcrio : 11. 

 Ili/cira," Arch. mikr. Anat. 20 l?d. 



§ C. F. Jicki'li, " Dor Bau der Ilydroidpoh-jion, I.," Morpliol. Jahrb. 

 Geji^oiibaur, 8 Ud. 



II Bedot, '' llccherchos sur let; crlhilcs urticautc.-," llccueil zoul. suisse, 

 t. iv. 



