REPORT ON THE NEMERTEA. 97 



region of the body where the dorsal musculature passes into the ventral, and where the 

 intervening layer of muscular tissue is either very thin or even (sometimes locally) 

 absent, at least as a special layer. In every transverse section some three or four of these 

 glandular flasks are simultaneously cut (PL XV. fig. 11). They show no further variety 

 of structure, but are not found along the whole length of the body. In the hinder half 

 at least I have not detected them. The histological constitution of these flask-shaped 

 glands is difiicult to make out in the spirit specimens. The epithelium clothing them 

 had a very much changed and deteriorated aspect, and only in certain favourable regions 

 could I deflnitely establish the fact that it was built up of largish cells with large nuclei 

 (PL XV. fig. 12), the contents of the cells being granular like those of the cells of the 

 median precerebral organ before described. Innervation was not so clearly traced here, 

 though in the head these flask-shaped organs certainly receive fibres from the very 

 numerous cerebral branches there present. 



Having once determined the presence of the organs just described and their situation, 

 it was found that their presence is even externally traceable in the specimens of Amjohi- 

 porus moseleyi (see PL IX. fig. 8) by a white line running backwards from the tip of the 

 head along the comparatively sharply edged margin of the body (see pp. 20, 21). When a 

 transverse section is made in this region with a razor, the naked ej^e can trace this white 

 line extending inwards for a short distance as if the pigment occasioning it were very 

 thickly applied. Viewed with the microscope, it is then easily seen that this white 

 spot breaks up into the accumulated flasks as above described, which are surrounded 

 and supported by the gelatinous tissue. In such a section the latter tissue is much more 

 transparent and homogeneous, thus bringing out the glands as white lateral spots in this 

 transparent imbedding mass, in which also the rest of the internal organs may be seen 

 to be suspended, and which is dorsally and ventrally limited by the body musculature 

 and the integument. 



It may finally be noticed that I have never succeeded in finding the necks of these 

 flasks that lead to the exterior wholly free and open, as I have the canal of the posterior 

 brain-lobe or the excretory duct of the nephridia. These very numerous necks of the 

 flask-shaped organs are always filled with a mass that has a streaked and fibrous appear- 

 ance. I mention this because it partly contributes to establish my conviction that the 

 physiological significance may indeed be glandular, and that the secreted, viscid mass, 

 passing out perhaps more copiously when the animals are immersed in spii-it, remains 

 fixed in this passage to the exterior. 



If it be not premature — as I consider it to be — to establish any comparison between 

 these organs and parts of the organism of Vertebrates, one would certainly be reminded 

 of those canals in the head which are known as the " Schleimcanale," and which are 

 continued along the sides of the body as the lateral line. The significance which of late 

 has been more and more definitely assigned to these organs in the Vertebrates, as 



(ZOOL. CHALL. EXP. — PART LIV. — 1887.) Hhh 13 



