106 Dr J. G. Allman on the 



On the Anatomy and Physiology of Cordylophora ; a contri- 

 bution to our knowledge of the Tubularian Zoophytes. 

 By George James Allman, M.D., M.R.I.A., Professor of 

 Botany in the University of Dublin, &c. 



The author, after pointing out the necessity of giving 

 greater definiteness to the terminology employed in the de- 

 scription of the true zoophytes, proceeds to the anatomical 

 details of Cordylophora, a genus of Tubulariadoz. He de- 

 monstrates that Cordylophora is essentially composed in all 

 its parts of two distinct membranes inclosing a cavity, a 

 structure which is common to all the Hydroida. For greater 

 precision in description, he finds it necessary to give to these 

 membranes special names, and he therefore employs for the 

 external the name of ectoderm, and for the internal that of 

 endoderm. Each of these membranes retains its primitive 

 cellular structure. In the ectoderm thread-cells are pro- 

 duced in great abundance ; these are formed in the interior 

 of the ectodermal cells by a process of endogenous cell-for- 

 mation, and are afterwards set free by the rupture of the 

 mother-cell. The thread-cells in a quiescent state are minute 

 ovoid capsules, but under the influence of irritation, an in- 

 ternal sac is protruded by a process of evagination ; the sur- 

 face of the evaginated sac is furnished with a circle of curved 

 spicula, and from its free extremity a delicate and long fila- 

 ment is emitted. The thread-cells of Cordylophora thus 

 closely resemble the " hastigerous organs" of Hydra. The 

 polypary is a simple unorganized secretion deposited in layers 

 from the ectoderm. In the endoderm the author points out 

 a distinct and well-developed glandular structure composed 

 of true secreting cells, which are themselves produced in the 

 interior of mother-cells, and elaborate a brown granular se- 

 cretion which he assumes as representing the biliary secre- 

 tion of the higher animals. He describes, as a system of 

 special muscles, certain longitudinal fibres, which may be 

 distinctly seen in close connection with the inner surface of 

 the ectoderm. The tentacula are shewn to be continuous 

 tubes communicating with the cavity of the stomach, and thus 



