360 EDWARD S. MORSE ON 



Another question must be asked : are the central and accessory vesicles related 

 organically ? They certainly appear to have a similar structure. In T. coreanica the 

 curious lainellated central organ, the so-called heart, is connected with the lateral vesicles 

 through a colored and glandular thickening of the edge of the ilio-parietal band. Now 

 this thickening is, I believe, associated with genital activity, and later I shall show that 

 the immediate region of the accessory hearts becomes changed during genital activity and 

 a number of glandular prominences make their appearance on the genital band at this 

 time. The central and accessory hearts appear so identical in structure and color that it 

 would seem they were related functionally. I shall discuss the accessory " hearts of 

 Hancock " under genitalia, but must remark here that these hearts appear in every case in 

 close proximity to the nephrostomes, and as these in the Testicardines appear at the 

 coelomic termination of the great pallial sinuses, the accessory hearts are found also in 

 close proximity to these terminations. Hancock represents them in Magellania flavescens 

 as attached to a band, the end of which is actually imbedded in the termination of the 

 pallial sinus. I have not observed this condition in associated forms. Hancock also 

 represents in M. flaoescens, four accessory vesicles, two dorsal and two ventral, corre- 

 sponding to the pallial sinuses, yet in this species there are only two nephridia. In If. 

 jixiftacea, there are four nephridia and also four accessory vesicles. In T. septentrionalis 

 there are four pallial sinuses, yet only two accessory vesicles. It is somewhat singular 

 that a careful study of Lingula, Glottidia, and Discinisca failed to reveal the presence 

 of any organ corresponding to the " heart of Hancock " or to the accessory hearts, though 

 the uephridia are conspicuous organs, as they are in all brachiopods ; on the other hand 

 there is no feature more constant than the pallial sinuses, yet with this constancy in 

 structure we find the " heart of Hancock " and the accessory heart, with few exceptions 

 in the Testicardines only. In other words, in those brachiopods in which the coelomic 

 cavity is contracted to the smallest space and the greater mass of the genitalia arise in the 

 pallial sinuses, the central and accessory vesicles are present, while in the Ecardine forms, 

 in which the coelomic cavity is capacious and the genitalia are confined to tin's cavity 

 alone, these vesicles are absent. I think, therefore, that the accessory vesicles at least, 

 may with reason be considered under genitalia and not under the circulatory apparatus. 



NEPHRIDIA. 



The paired oviducts in Brachiopoda are so identical in form, attachment, and 

 function with similar organs in the chaetopod worms that I formerly designated them 

 segmeutal organs from the name first given by Williams ('51), to the oviducts of annelids. 



