LIVING BRACHIOPODA. 

 Cirri. 



335 



The cirri of the U,igvMdae thus far observed are tubuhar to their tips and the blood 

 circulates freely within this cavity, as shown in a cirrus of Glottidia (46: 2) . The cirri 

 are strongly cihated and the ciliary movements must be vigorous to cause the rapid 

 currents of water which steadily pass in and out of the pallial chamljcr (40: 1-2). The 

 cirrus of Glotticha is marked by irregular transverse wrinkles which are repeated on the 

 Uning membrane of the cavity within, giving it the appearance of a rude sort of annula- 

 tion The walls of the cirrus are thick and the tubular cavity within has nearly the same 

 diameter as the thickness of the wall. In L. anatina, the cirri are coarsely and densely 



ciliated. 



In all Ecardine brachiopods the cirri are colored in various parts. In Glottidia, the 

 tip of the cirrus has a light brown tinge (39: 7) . In L. hpidala, it is brown on the out- 

 side from the base to a third of its length; near the tip a brown tint is seen on the inner 

 surface (39:2; 45:15; 46:5). In L. anatina, the sides of the cirrus are brown. The 

 structure of the cirrus in Discinisca seems more complex than that of the Lmguhdae. 

 The cirri in the Testicardine group are usually white or yellowish, though Schulgin ('84) 

 fio-ures the cirri of CisteUa kowalemhn as yellowish red, and these he represents as pro- 

 ie°ctino- shcditly beyond the borders of the shell. He furthermore adds that he never saw 

 a particle of blood enter them. The cirri of many Testicardine forms have already been 

 figured and described, notably by Bemmelen ('83), who has, with infinite pains, given a 

 most exhaustive series of drawings and descriptions illustrating the histology of a number 



of brachiopods. 



At 46 ■ IS./ is represented a portion of a cirrus much enlarged of //. psdtacea. in dis- 

 section, it appears almost cartilaginous, so stiff and rigid does it seem. The ciliated 

 epithelium is easily detached from the surface. A narrow inner tube is found m which 

 the blood freely circulates ; outside this tube is a sheath containing encirchng muscle 

 fibres, and outside of all is the firm cartilaginous-appearing substance which supports 

 the loosely connected ciliated epithelium. 



Schuluin, in the paper above referred to, described the cirrus of CisteUa as having a 

 somewhat firm exterior, which is elastic, and said that when the cirrus is bent by muscular 

 contraction, the elasticity of this substance brings it back to position again. It has 

 occurred to me that the cirrus of //. psittacea may act in the same way. There are no 

 spiculae in the cirri, as in Terebratulina and allied forms, and though more complex m 

 structure than the cirri of the LlnguUdae, they bear a nearer relation to these than to 

 those of the Testicardines. Hemithyris in other respects also approaches the Ecardine 

 group. 



