EXCRETOEY TUBULES IN AMPHIOXUS LANCEOLATUS. 491 



the bar^ and communicating, as is seen from fig. 4, with the 

 dorsal aorta. This vessel then separates either entirely into 

 two parallel trunks, or is only constricted medianly, so that 

 we find one vessel running below the median inner epithelial 

 band, and the other one on the inner face of the chitinoid rod, 

 as figured by Professor Lankester. In the case of the secon- 

 dary or tongue bars carmine is found also within the hollow 

 of the chitinoid rod, so that I think Schneider's conception of 

 this space as a blood-vessel connected with the one running 

 along the inner surface of the rod is probably correct. A 

 very small vessel seems to run on the outer edge of the 

 chitinoid rod. It would seem to be connected with the blood- 

 vessel runniug beneath the excreting tubule in fig. 1, and 

 being like those in the suspensory folds connected with the 

 excretory function of the atrial epithelium. The two dorsal 

 aortse are either connected at intervals by very fine vessels, or 

 else each gives off branches which run beneath the epithelium 

 of the dorsal groove of the pharynx. 



Besides these branches of the aortae I was able to confirm 

 Schneider's statement that branches are given off to the 

 muscles of the body, passing up by the side of the notochord, 

 and other branches to the inner face of the body-wall. These 

 latter branches run beneath the ccelomic epithelium, and more 

 ventrally beneath the atrial epithelium; they connect the 

 dorsal aorta with a longitudinal vessel described by Miiller as 

 running on the inner body-wall above the gonads. 



Indeed, the whole inner surface of the atrium seems very 

 well supplied with blood-vessels running beneath the atrial 

 epithelium, and in the case of these modified epithelial cells, 

 described by Miiller as possibly renal organs, diverticula are 

 formed by the blood-vessel between the cells (fig. 6). 



Along the inner lamella of cutis, too, of the ventral atrial 

 wall I found a considerable amount of carmine in what I con- 

 clude must be a blood-vessel or a vascular space. I have not 

 here given a general account of the vascular system of Amphi- 

 oxus, but have confirmed statements by various observers, 

 statements which Professor Lankester in his last memoir has 



