i9o8.] EXCRETORY ORGANS OF METAZOA. 595 



not have been so formed, but would rather seem to be ectoblastic 

 hke the ^lalpighian vessels in Insects. 



Unicellular Glands of the Intestine. — Nalepa (1888) has de- 

 scribed for Phytopids three large unicellular glands in connection 

 with the rectum, and supposed they may be excretory. 



Co.val Gla}ids. — In Liuinocharis Thon (1905) found a pair of 

 glands in the region of the second coxae; in Eulais they are most 

 active in the nymphal stage while they degenerate in the adult (by 

 substitution of the proctodaeal organ), but in Liinnocliares they 

 function even in late life. Supposed coxal glands have also been 

 described by With (1904) for the Notostigmata, by Sturany (1891) 

 for Trombidium, by Winkler (1888) for Gamasidoe, and by Alichsel 

 (1883) for Oribatids. The lateral abdominal glands of Gamasids, 

 Tyroglyphids and Oribatids may be homodynamous. The develop- 

 ment of these various glands seems to be quite unknown, so that 

 nothing can be said of their homologies. 



35. Leptocardii.^° 

 The nephridia in Amphioxns were discovered by Weiss (1890) 

 and particularly described by Boveri (1892"). The latter found 

 them to be segmentally arranged, in about ninety pairs in the 

 branchial region, there being one pair to every two branchial arches. 

 Each nephridium was described by Boveri as a canal with one open- 

 ing into the ectoblastic atrium, and several into the coelom (sub- 

 chordal cavity) ; inserting into the orifice of each of these nephro- 

 stomes, but not into that of the nephridiopore, is a tuft of long 

 Fadenzellen. Goodrich (1902) has reinvestigated these organs, 

 and while he confirmed the preceding account in most particulars, 

 he found that the Fadenzellen are solenocytes, each hollow with a 

 long cilium and each closed from the body cavity, and that there 

 are no open communications of nephridia with the crelom : " These 

 tubules are situated ' morphologically ' outside the coelom, being 

 covered with coelomic epithelium ; the solenocytes alone push 

 through into the ccelomic cavity." And he concluded " that in their 



" The Leptocardii exhibit so man\' morphological peculiarities that they 

 are to be removed from the group of the Vertebrata ; the Craniota by them- 

 selves compose a homogeneous assemblage. 



