ON APPENDICULARIA FLABELLUM 457 



however, an interval in which the heart is situated. The right lobe is 

 quadrate in outline, and undivided, but the left is irregular and lobu- 

 lated. The inner surface of the stomach is papillose and ciliated, and 

 many yellowish granules are scattered through the substance of its 

 walls. The intestine arises from the upper angle of its left lobe, bends 

 to the right, and then, when it reaches the middle line, passes forward 

 to the anal aperture. The rectum is ciliated, and, as before, I was 

 unable to find any trace of the tubular "hepatic" system, so general 

 among the other Ascidians. 



The heart (o) is large, and occupies a transverse position between 

 the two lobes of the stomach, laterally, being more closely in contact 

 with the right lobe, and the testis and base of the caudal appendage, 

 antero-posteriorly. I was unable to observe any blood corpuscles, nor 

 could I discover any sign of that reversal of the direction of the con- 

 tractions so general among the other Ascidians. The absence of 

 corpuscles would have rendered it almost impossible, under ordinary 

 circumstances, to discover the direction of the circulating currents, but 

 in one individual, the testis, having attained its full development, had 

 broken up within the body, and the sinuses were filled with dark 

 masses of spermatozoa. The heart, in full action, propelled these in 

 a regular course up one side of the caudal appendage and down on 

 the other (Miiller has already described such a current in his 

 * Vexillaria '), forwards on the hjemal side, and backwards to the heart 

 on the neural side. This individual was particularly instructive also, 

 by affording corroborative evidence as to the nature of the pharyngeal 

 canals. Had these been in any way connected with the sinus system, 

 as Gegenbaur supposes, the spermatozoa could hardly have failed to 

 pass into them. Nothing of the sort occurred however ; they passed 

 round in the sinus between the walls of these canals and the outer 

 tunic without the slightest extravasation, and their dark hue gave the 

 contour of the canals only a better definition than it had before. 



The testis was always present ; small, discoid, and apparently 

 attached by minute radiating filaments to the parietes in the younger 

 specimens, it assumed the bilobed form in the larger ones, occupying 

 a large space behind the alimentary canal. Individuals with fully- 

 developed spermatozoa were comparatively rare. In that just referred 

 to, the spermatozoa had rod-like heads, about i -7000th of an inch 

 long, with very long, delicate, and filiform tails ; and the testis was 

 reduced to a mere transverse band, the greater part of its substance 

 having apparently been shed in the form of spermatozoa. Of a vas 

 deferens I could find no trace. 



The rounded bodies {111) on each side of the branchial cavity 



