LIVING BRACHIOPODA. 335 



CIRRI. 



The cirri of the lAngulidae thus far observed are tubular to their tips aud tlie blood 

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

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

 currents of water which steadily pass in and out of the pallial chamber (40:12). The 

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

 lining 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. lepidula, 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 Disciuisca seems more complex than that of the. LimjuJidfie. 

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

 figures the cirri of ClsteUa kowafcvxkii as yellowish red, and these he represents as pro- 

 jecting slightly 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 Bemmeleu ('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: 18" is represented a portion of a cirrus much enlarged of H.psittacea. 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 in which 

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

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

 the loosely connected ciliated epithelium. 



Schulgin, in the paper above referred to, described the cirrus of Cistella 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 H. psittacea may act in the same way. There are no 

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

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

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

 group. 



