388 



of tubularia was mentioned by Bickfürd^), Driesch^) and in 

 two récent papers by Morgan') but. I think, it bas not yet been 

 sufficiently examined. We do not find in tbe literature the bistolo- 

 gical study of this process. Morgan (02) says in bis second pa- 

 per tbat. wben pièces of tbe stem are eut longitudinal!}', „in the 

 course of a few minutes tbe coenosarc witbdraws sligbtly from 

 the eut end of the perisarc and then" a tbin membrane develops 

 that ultimately closes the end". „This membrane is composed of 

 ectoderm on its outer and endoderm on its inner surface". 



The development of hydrantbs. wben tbe stem is eut longi- 

 tudinally, is also not sufficientl}' described. It was mentioned by 

 Driescb (97) and Morgan (01). But Morgan biraself stated bis 

 esperiment were not complète *}. 



This work was done during my stay at tbe Naples Zoologi- 

 cal Station. 



In my experiments tbe stem of tubularia was eut in two lon- 



gitudinally. Two half-cylinders were 

 obtained in this way. Tbey are com- 

 posed of the perisarc (fig. 1. p) on the 

 outer and coenosarc (fig. 1. c) (ecto- 

 derm and endoderm) on tbe inner 

 surface. The central carity of the stem 

 is now open. 



Fig. 1. The first process which we can 



observe is tbe formation of the new 



cavity. This pi-ocess is not in ail cases a process of closing over 



of tbe old cavity but as we shall see sometimes a new cavity is 



foi-med. 



There are manv difficulties in Splitting tubularia so that both 



MBickford Elizabeth E. Notes on Keg'eneiation and Heteromorpliosis of 

 Tubularia Hydroids. Journ. of Morphology, Vol. IX. 18h4. 



') Driesch H. Stadien über Kegulationsvermögen der Organismen. I. Von 

 den regulativen W'achsthums- und Ditierenzierungsfähigkeiten der Tubularia. Arcb. 

 f. Entwickelungsmecbanik. Bd. V. 189V. 



') Morgan T. H. Kegeneration in Tubularia. Arch. für Entwickelungs- 

 mechanik. Bd. XI. 1901. 



Morgan T. H. Fnrther Experiments on the Regeneration of Tubularia. 

 Arch. für Entwickelungsmecbanik. Bd. XIII. 1902. 



*) „A further study of these longitudinal pièces will, 1 thiuk, fuUy repay 

 the investigator". (Morgan, Ol, p. 366). 



