SCHULZe's memoir on CORDYLOPHORA LACUSTRIS. 37 



Notwithstanding our author's very reliable method of in- 

 vestigation, I am not prepared to relinquish my belief in 

 these secondary cells, more especially as I believe my conclu- 

 sions supported by an examination of other hydroids, though 

 Schulze could no more find them in Hydra than in Coi'dy- 

 lophora. It is by no means impossible that their existence 

 may depend on conditions of nutrition, and that they may 

 be present at certain times in the life of the hydroid and 

 absent at others. 



The author is inclined to regard the free ends of the en- 

 dodermal cells as destitute of membrane, and believes that 

 the protoplasm which is accumulated at this spot has its 

 surface freely exposed to the lumen of the stomach and of 

 the co^nosarc, an important and interesting fact if confirmed 

 by subsequent observations. 



He has also succeeded in clearly establishing the presence 

 of cilia over the whole of the endoderm of the somatic 

 cavity, each of the endodermal cells carrying a single long 

 fine cilium on its free surface. 



Those cilia had entirely escaped me in my original inves- 

 tigation of Cordylophoi'a, but I have since found them very 

 distinct in other hydroids, and have long been convinced 

 that my failure to discover them in Cordylopliora was owing 

 to the imperfection of the means of investigation then at my 

 disposal. The researches of Kolliker have also shown 

 their general distribution in the Hydroida. Schulze and 

 lieichert have seen them in Hydra, where I have been more 

 doubtful of their presence than in other hydroids. 



The existence of the longitudinal ridges which I have de- 

 scribed in the stomach- walls of Cordylophora has not been 

 confirmed by Schulze, who regards the appearance of these 

 ridges as accidental and merely the result of the contraction 

 of the stomach-walls. There can be no doubt, however, of 

 the presence of more or less definite rugae in the endoderm 

 of the stomach of other hydroids, though in extreme dilation 

 of this cavity they may become nearly effaced, and I cannot 

 help thinking that their absence in the specimens of Cordy- 

 lophora examined by Schulze was owing to their obliteration 

 by the undue mechanical extension to which the surface 

 under examination was subjected. 



The structure of the tentacles of Cordylopliora has espe- 

 cially engaged our author's attention, and he denies the ex- 

 istence in them of the continuous axial cavity, which I at 

 one time believed to characterise them. In this I am ready 

 to concur with him. I have long since given up the idea ui 

 a continuous cavity running through the whole length of tlv; 



