On the Structure of the Excretory Organs of Amphioxus. Part 2.—The ...

More documents

Recommendations

Info

188 EDWIN S. GOODRICH. In other regions of the canal they may be more sparsely distributed. Cell outlines are rarely visible. The cytoplasm sol. cep :ep .... bv. -ch. Diagram of a section through the nephridium, passing along a X>lane at right angles to the long axis of the animal, and parallel to the gill bar. a. e. Atrial epithelium, h. Base of secondary gill-bar, bv. Blood-vessel, c. ep. Coeloinic epithelium, ch. Chamber containing solenocytes. n. Wall of nephridial canal, op. Nephridiopore. sol. Solenocyte cell, and t. its tube containing ;i flagellum. usually contains numerous granules of an excretory nature. As we approach the tip of a diverticulum, we find that the
STRUCTURE OP THE EXCRETORY ORGANS OE A3IPHIOXOS. 189 nuclei do not gradually decrease in number, but suddenly stop in the immediate neighbourhood of the solenocyte tubes (figs. 6, 20). Here, where these tubes spring out of the canal, there are no nuclei; but the wall itself is continued as a sheet of more or less granular cytoplasm completely closing off the lumen of the canal (figs. 6, 9, 20, 21). This canal wall may be thick or thin, the variation in thickness depending, I believe, chiefly on the state of tension of the fluid inside the canal. In good thin sections the wall is always visible. Indeed, the better the section, and the more perfect the stain, the clearer becomes the limiting wall, whatever may be the direction in which it is cut. Figs. 19 and 20 represent two sections takeu parallel to the surface of the nephridiutn, sagittal sections of the animal. The first just shaves through the outer wall of the canal, and shows many solenocytes lying on the blood-vessel. The second, which ouly corresponds to the left hand portion of the first figure, cuts deeper into the canal through the extremity of one of the branches, where may be seen the solenocyte tubes piercing the closing wall. In the nest section the nuclei of the opposite side begin to appear, the whole thickness of the small solenocyte-bearing offshoot having been nearly cut through. The following section would show only a slice of the wall. There is no opening. Fig. 21 gives a similar view of another nephridium in the same animal. Two consecutive sections through the lowermost tip of the anterior limb of the nephridinm are drawn in figs. 13, 14. Here again are seen the tubes piercing the wall, in which there is no trace of an opening. Figs. 5 and 6 represent sections from a series nearly transverse to the animal and parallel to the bar. That in fig. 5 passes through the external pore, and shaves off the wall of a diverticulum. The next section (fig. 6) cuts through the extremity of this diverticulum. It is seen that the lumen is closed off from the cceloni by a distinct cytoplasmic wall, through which pass solenocyte tubes. In fig. 7 is drawn a portion of the same section when the microscope has been VOL. 54, PAST 2. NEW SERIES. 14
Page 1 and 2: STRUCTURE OF THK EXCRETORY ORGANS O
Page 3: STRUCTURE OF THE EXCRETORY ORGANS O
Page 7 and 8: STRUCTURE OF THE EXCRETORY ORGANS O
Page 9 and 10: STItUCTCJBK 01' THK EXCKRTOIiY 01WA
Page 11 and 12: STRUOTUBK (.)!
Page 13 and 14: STRUCTURE 0.1;' THE EXCRETORY ORGAN
Page 15 and 16: STRUCTURE 01? THE EXCRETORY OHG-ANS
Page 17 and 18: STRUOTUBE OP THE EXCRETORY ORGANS 0
Page 19 and 20: STRUCTURE OF THE EXCKJETORY ORGANS
Page 21: STRUCTURE OP THE EXCRETORY ORGANS O

On the Structure of the Excretory Organs of Amphioxus. Part 2.—The ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?