Morse.] 336 [March 19, 
In Lingula this membrane appears to extend into the pallial 
sinuses, as is probably the case with other Brachiopods. At all 
events, the circulation in Lingula is induced by ciliary action, as can 
be plainly seen through the transparent shell of Lingula pyramidata, 
and this fluid is that of the perivisceral cavity, and is corpusculated. 
Carl Semper,! in his studies of Lingula anatina, says, that in that 
species there is no heart proper, and that the blood is propelled 
through the vessels by vibratile cilia. As early as the year 1862, he 
gave particulars, and has repeatedly insisted upon this anomalous 
state of things. 
To John B. Macdonald, however, belongs the credit of first calling 
attention to these peculiarities in Lingula. 
In the year 1861, Mr. Macdonald? announced the discovery “ of a 
determinate circulation of spherical and violet-tinted corpuscles in all 
the ramifications of the pallial sinuses, not dependent on the contrac- 
tions of a pallial cavity, but upon the undulations of a ciliary lining.” 
The vascular system described by Hancock, with a vessel upon the 
dorsal surface of the intestine, I have never succeeded in studying 
satisfactorily. In Lingula pyramidata I have not been able to find 
the vescicle upon the back of the intestine, but the vessel I have 
clearly made out. In Discina I] have made out the vescicle. This dif- 
ficulty of finding a heart has been shared by others. Carl Semper 
could not find it, and Dr. Lancaster in the February number of the 
Annals and Magazine of Natural History for 1873, p. 93, says in regard 
to Terebratula vitrea: ‘I entirely failed to convince myself that the 
organ regarded by Mr. Hancock as a heart really has the function 
of one in T. vitrea. I repeatedly opened fresh specimens with 
rapidity, in order to witness its contractions, if any, but never saw 
such contractions ; nor could I find vessels in connection with it, 
nor evidence that it had muscular walls. Dr. Krohn, of Bonn, had 
equally been unable to obtain evidence that this curious little dila- 
tation has the function of a heart.” From injected specimens of 
Lingula, and from observations on living Terebratulina and Rhyncho- 
1 Zeitschr. fir Wissensch. Zool., XIv., p. 424. 
2 On the Physiology of the Pallial Sinuses of the Brachiopoda. Trans. Linnean 
Soc. XXIII., p. 3/3, plate XxXXv. / 
3 In a late study of living Terebratulina I observed a distinct circulation going 
on in the sinuses of the pallial membrane, but whether these currents were induced 
by ciliary action I failed to make out. The fact, however, that the delicate mem- 
branes in the perivisceral cavity are clothed with cilia, I clearly established. 
