1880. | Development of Amphioxus lanceolatus. 81 
discovered to exist upon the floor of the posterior portion of the 
branchium near the branchiopore, and as no other function could 
be thought of as being performed by them, and as there were, 
apparently, no other organs which might subserve the purposes of 
excretion, it was supposed that these patches acted in this 
capacity, and after eliminating the urinary products cast them 
into the branchium to be extruded from the body through the 
branchiopore with the water which passed from this orifice. 
This opinion, which might be considered as very plausible, 
since the patches were associated in position with the posterior 
generative bodies, was very generally held until quite recently, 
but in the paper by Prof. Lankester, already referred to, he 
announces the discovery of certain canals which he considers as 
representing, rather than these patches, the true urinary ducts of 
Amphioxus. These vessels, one upon either side, are in the form 
of long tubular ridges, formed along the roof of the pleuro- — 
peritoneal portion of the branchium as outgrowths from the meso- 
derm of the body walls. They are composed of pigmented cells 
and their posterior extremities are open and communicate with 
the branchium near the branchiopore, but their anterior extremi- 
ties, which are in the neighborhood of the sides of the pharynx, 
are probably closed. These canals are thus apparently homolo- 
gous with the earlier stages at least of the ducts of the uriniferous 
tubules of other vertebrates, and, unless further investigation : 
shows them to appertain unmistakably to some other system they 
will undoubtedly henceforth be considered as representing, as- 
Prof. Lankester suggests, the urinary system of this animal. . 
The Blood Vessels—The general arrangement of the vessels of- 
the blood system in Amphioxus is very similar to that found’ in 
the young of all osseous fishes, but in the minutiæ of the plan 
there are quite important modifications, which, although not 
making a complicated system, yet render it very different from 
ns other ktiown among vertebrates. The main blood vessel, or ž 
: vein, extends from the anus along the ventral aspect of the intes- — i 
tine to the base of the saccular liver, thence around the entire — ae 
length of this organ upon both ventral and dorsal edges, to con- 
“ene along the ventral aspect of the cesophagus‘and pharynx to 
* point just beneath the first branchial cleft where it expands or 
: Merges into a bulbous organ, the heart. This canal is pulsatile, 
— Pos 1 has been given different names according to the 
