TRANSACTIONS OF SECTION D. 689 



identical in appearance with those of the stomodaeum. With the exception of 

 the genus Xenia the occurrence of gland cells in the stomodseum has not hitherto 

 been recorded in any other member of the family. I have, however, observed 

 them in every other genus which I have had the opportunity of examining ; it is 

 therefore very probable that they occur throughout the family. 



The secretion from the gland cells, combined with the pressure exerted by 

 the mesenterial filaments, breaks up the food into minute particles, which are 

 ingested and subsequently digested by the amccboid endoderm cells of the ventral 

 and lateral mesenterial filaments. Particles of food which escape the filaments 

 are apparently taken up by the amoeboid endoderm cells lining the coelentron 

 and canals. 



3. Distribution of Nidriment. — I have observed the stellate cells, which com- 

 pose the so-called ' mesogloeal nerve-plexus,' to withdraw and thrust out the 

 processes which have been called ' nerve-fibrjls,' and by this means change their 

 shape and position. These cells therefore are amceboid. 



After squirting clouds of finely powdered carmine about the extended tentacles 

 of expanded zooids for several days, particles of carmine were observed to be 

 present • (1) in the amceboid endoderm cells of the ventral and lateral mesen- 

 terial filaments and coelentron ; (2) in the amceboid colls of the endodermal 

 canals; (3) in the stellate cells comprising the so-called 'nerve-plexus,' which 

 I have observed to be amceboid. 



The amceboid endoderm cells containing carmine particles were observed to 

 thrust out processes into the mesoglcea and to assume a condition identical in 

 appearance with the stellate cells composing the ' nerve-plexus.' 



I would therefore suggest that the distribution of nutriment is effected in the 

 following manner. Certain amceboid endoderm cells loaded with nutriment 

 wander or have wandered into the mesoglcea, where they form an amceboid 

 plexus of cords and strands of cells which extends throughout the colony. The 

 intimate connection between the digestive endoderm cells of the zooids and the 

 plexus is maintained. If we suppose that throughout the plexus the nutritive 

 protoplasm may be transferred from cell to cell— and the presence of carmine 

 particles in the mesogloeal plexus affords substantial evidence for believing this 

 to be the case — then this system of amceboid cells must be regarded as a mdritive 

 plexus, and by its means nutriment may be conveyed from the digestive endoderm 

 cells of the zooids to every portion of the colony. 



7. On the Origin of the JSpiphysis in Amphibia as a Bilateral Structure. 



^y John Cameron, ilf.& 



In very early embryos of Amphibia (Rana, Bufo, Triton), the epiphysis is found 

 to develop in the form of two small recesses or outgrowths from the roof of the 

 fore-brain, which are placed on either side of the mesial plane. The right recess 

 terminates its existence by blending with the more rapidly developing left recess. 

 This active growth on the part of the latter causes the epiphysial opening to 

 becomesituated to the lefc of the mesial plane in the majority of cases. These 

 above observations in the case of the amphibia, correspond in many ways with 

 those of Beraneck, Dendy, Gaskell, and Locy in other vertebrate types. During 

 the later stages of development in amphibia there are distinct evidences of the 

 bilateral origin of the epiphysis; for the portion in relationship to the superior 

 commissure (fibres from which form the nerve-supply of the pineal eye), along 

 with the part distal to this, together correspond to the pineal eye of liatteria, 

 while the remainder of the proximal portion which communicates with the thala- 

 mencephalon, corresponds to the epiphysial stalk of Ifatteria. The degenerative 

 condition of the amphibian epiphysis is probably due to this blending together of 

 the right and left primary recesses — the result of this being that they mutually 

 interfere with one another's growth. This observation is supported by the fact 

 that the left epiphysial outgrowth in Hatteria (according to Dendy) remains 



1903. T Y 



