1884.] On Limnocodium Sowerbii, Allman and Lankester, 9 



mesentery of the transverse colon before it becomes related to the 

 omentum). The colic arteries are briefly dismissed with the excep- 

 tion of the middle ; this vessel is discussed at greater length 

 owing to the doubts which exist concerning the development and 

 Anatomy of the transverse mesocolon. An attempt is made to 

 refute the adhesion theory advocated by Haller, and to explain how 

 it is quite possible for the mesocolon to consist of two layers instead 

 .of four. 



In conclusion the following principles are deduced : — 



First. That the arteries of the abdomen, including the splenic and 



hepatic, were originally derived from the dorsal aorta for the supply 



of the midgut. 



Second. That they reach their destinations by passing through the 

 mesentery. 



Third. That they participate in all the changes the mesentery 

 undergoes. 



Fourth. That if an organ is developed in the mesentery or from 

 the gut, it will obtain part at least of its blood supply from the 

 vessels of the mesentery or gut, and that these will conform to the 

 preceding rules. 



It is finally remarked that although these observations have only 

 been applied to the human subject, yet they appear so simple and so 

 likely to be true that it is probable that they have a much wider 

 applicability. 



IV. "On the Occurrence of a Hydroid Phase of Limnocodium 

 Sowerbii, Allman and Lankester. By Alfred Gibbs 

 Bourne, Assistant Professor of Zoology in University 

 College, London. Communicated by E. Ray Lankester, 

 M.A., F.R,S. Received December 8, 1884. 



It is now four and a-half years since the Medusae of Limnocodium 

 were discovered by Mr. Sowerby, in the Victoria tank in the gardens 

 of the Royal Botanic Society, at Regent's Park. 



Since that time Professor Lankester has continued to make obser- 

 vations and experiments, in which I have assisted, with the view of 

 elucidating their life-history and the conditions of their somewhat ano- 

 malous occurrence. We discovered, however, nothing which threw any 

 light upon the subject. On November 27th Ave had an opportunity of 

 seeing the tank at the Botanical Gardens, immediately after the with- 

 drawal of the water, and I then collected and examined at Professor 

 Lankester's request a large quantity of the sediment and portions of 

 various roots and other submerged objects. 



