STRUCTURE OP THE EXCRETORY ORCxANS OF AMPHIOXUS. 205 
Fxg. 28. — Small poi-tion of a transverse section of the head, showing 
Hatschek's nephridium. Cam. L. oil-imm., oc. 3. 
Fig. 29. — Similar view of a larva (the same as that in fig. 2t, from 
Helgoland, with about thirteen gill-slits). Cam. L oil-imm., oc. 3. 
Fig. 30. — Portion of a longitudinal section of a larva, showing a 
nephridium opening behind the last open gill-slit. Cam. Z. 2 mm. ap. 
oil-imm., oc. 4. 
Fig. 31. — Portion of a longitudinal section of a larva, showing the 
fan-like group of solenocytes on the aorta. Cam. Z. 2 mm. ap. oil-imm., 
oc. 4. 
PLATE 15. 
Fig. 32. — Left side view of a larva, drawn fi-om living and preserved 
specimens. 
Fig. 33. — Left side view of the anterior region of a slightly older 
larva on a larger scale, from living and preserved specimens. The cilia 
are not indicated. 
Fig. 34. — Left side view of the posterior branchial region of a larva, 
showing the disposition of the solenocytes. From the living. 
Fig. ,35. — Ventral view of a region of a larva, showing the last open 
gill-slit, and two more jio.sterior nephridia. From the living. 
Fig. 36. — Ventral view of two posterior gill-slits of a living laiwa. 
Fig. 37 —Solenocytes from Hatschek's nephridium in the larva. 
Fig. 38. — Optical section of Hatschek’s nephridium in the larva. 
From the living. 
Fig. 39. — Ventral view of a nephridium showing its opening just 
within the margin of a posterior gill-slit in a larva. Solenocytes cut 
short. 
PLATE 16. 
Fig. 40. — Left side view of a single nephridium in a larva. From 
the living. 
Fig. 41. — Portion of a transverse section of a laiwa, passing through 
the nephridiopore. Cam. Z. 2 mm. ap. oil-imm., oc. 4. 
Figs. 42, 43, and 44. — Portions of three transverse sections of the 
head of the adult, showing Hatschek’s nephridium. In front of the 
ciliated pit (fig. 42), at the level of the ciliated pit (fig. 43), and behind 
it (fig. 44). 
VOL. 54, PART 2. — NEW SERIES. 
15 
