EXCEETORY TUBULES IN AMPHIOXUS LANOEOLATUS. 497 



EXPLANATION OF PLATES XXXIV & XXXV, 



Illustrating Mr. F. Ernest Weiss^s paper on the '' Excretory 

 Tubules in Amphioxus lanceolatus." 



PLATE XXXIV. 



Fig. 1. — Portion of a section through the pharyngeal region of Amphioxus, 

 showing the right dorso-pharyngeal coelom and an excretory tubule cut 

 longitudinally. A blood-vessel coloured by the carmine runs on the inside of 

 the tubule. 



Fig. 2. — The next sectiouj showing the beginning of the upward bending 

 of the tubule. In these and the following sections some carmine is seen in 

 the dorsal aorta. 



Fig. 3. — This section shows the origin of the blood-vessel lying beneath 

 the subexcretory tubule in Fig. 1 from the dorsal aorta. The atrial epithe- 

 lium of the secondary gill bar also shows excreted carmine, though to a 

 slighter extent than the tubule. 



Fig. 4 shows the opening of the excretory tubule into the upward exten- 

 sion of the atrium at the commencement of the secondary gill bar. It shows 

 also the branching from the dorsal aorta of the blood-vessel of the secondary 

 gill bar, and of the blood-vessel to the excretory tubule. 



In Figs. 3 and 4 can be seen the communication between the ccelomic 

 cavity of the primary gill bar and the dorso-pharyngeal ccelom. 



PLATE XXXV. 



Fig. 5 shows the portion of the excretory tubule behind its opening into 

 the atrium. 



Fig. 6 shows the thickened patches of atrial epithelium in the hind region 

 of the atrium described by Johannes Miiller. Their cells contain excreted 

 carmine granules. Below them is a blood-filled sinus, or possibly a network 

 of closed vessels, with processes running up into the thickened portions. 



Figs. 7 and 8 show an excretory tubule on the left side of the pharyngeal 

 region, and the opening of the tubule at the origin of the secondary gill bar. 



