6-1 SUMMARY OF CURRENT RESEARCHES RELATING TO 



to the elements of endodermal origin (muscles, tfec.). The Chrotognatha 

 present ns with one iutcrmcdiate condition which is very instructive ; 

 in them the nervous system, as has been shown by 0. Hertwig, con- 

 sists of an epidermic portion connected with the sensory fibres, and an 

 intermuscular portion formed by central organs and peripheral motor 

 elements. The epidermic portion is altogether comparable to that of 

 Actinia. Hertwig thinks that we may regard the intermuscular 

 nervous system of Sagitia as comparable to that which is found under 

 the intermediate membrane in the sea-anemone ; and Fraipout thinks 

 that this homologisation is justifiable. 



If we go a step further, we may regard the brain and ventral cord 

 of Protodrilus as answering to the supra-oesnphageal connected with 

 the ventral ganglion in Sagitfa ; but what, then, has become of the 

 ectodermal plexus of Sagitta in the Annelids '? It has disappeared 

 as such in the Archiannelides, but its constituent elements are pro- 

 bably to be found on the ventral surface of the medulla. It has no 

 raison d'etre the moment there are no ectodermic muscles. The 

 author thinks that we must consider the membrane which, in Poly- 

 gordius, separates the epidermis from the longitudinal muscular areaa, 

 as representing the ectodermic muscular layer of the Actinioi ; and 

 this view is confirmed by the developmental history of Snrcocirrus. 



The question now arises, how did the very intimate relations which 

 exist between the elements of the epidermis and the intermuscular 

 plexus arise in the Archiannelids, seeing they were not formed 

 primitively in the Ccclenterata. If the plexus and the intermuscular 

 nervous centres of the Chjetognaths and Annelids have the same 

 origin as the muscles, the relations between them and the ectodermal 

 elements must be secondary ; they may have appeared in consequence 

 of the atrophy of the ectodermal muscles. Later on there would be a 

 condensation of the ectodermal plexus on the ventral surface, but this 

 localization would not necessarily result in the complete interruption 

 between the cells of the surface of the epidermis and the intermuscular 

 plexus. A certain number of ectodermal cells would remain in 

 relation with the plexus without there being any change in the func- 

 tion of the dilFerent elements. We should thus find in the lower 

 Annelids a permanent arrangement, which would be transitional 

 between what obtains in the Chaetognatha on the one hand, and the 

 Chaetopoda on the other. 



In presenting this hypothesis the author does not wish to be 

 supposed to think the Annelids are derived from the Chfetognatha, 

 but he thinks that he has shown that it is possible to connect phylo- 

 genetically the nervous system of the lower Annelids with that of the 

 Actiniaria by means of the Cha^tognatha, and so to associate the 

 facts given by Hertwig with the hypothesis propounded by Sedgwick. 



Respiration of the Serpulacese in Relation to their Tegumentary 

 Pigments.* — L. Orley is not satisfied with a knowledge of the nature 

 of colouring matters, but thinks that positive conclusions as to their 

 functions can only be obtained when the 'vital processes of their 



• Termeszft. Fiizetek., viii. (1884) pp. 199-207. 



