made at Naples in the winter o/* 1871-72. 93 



dividually movable, though rarely moved. Each cirrus 

 cori'esponds in essential structure as to its tubular character, 

 its horny and calcareous skeleton, and the circulation within 

 it of the blood, with a tube of certain Lamellibranchs' gills. In 

 young Pisidium pusillum the gills originate as three (in- 

 creasing in number) pairs of tubular processes. In young 

 Anomia they equally retain their character as a series of 

 isolated tubules ciliated on the surface. In young Terehratula 

 vitrea I found nine pairs of tubular tentacles (wonderfully like 

 the tentacles of a Pedicellina) ; and in the adult we have an 

 immense series of them, which only require to become adhe- 

 rent in order to give the essential structure of the Lamelli- 

 branch's gill-plate. 



The blindness in relation to the intestine of Terehratula 

 vitrea is certainly in that Brachiopod's rectum. There is no 

 anus, but a blunt cjecal termination. 



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 connexion with it, nor 

 evidence that it had muscular walls. Dr. Krohn, of Bonn, 

 had equally been unable to obtain evidence that this curious 

 little dilatation has the function of a heart. 



The " segment-organs " or oviducts (hearts of Owen) pre- 

 sented a beautiful appearance in the living state, on account of 

 their ciliation. It was possible to preserve them mounted in 

 balsam and also in osmic acid. 



The ovaries, lying as they do on the inner surface of the body- 

 wall (which is beautifully marked with calcareous spicula), may 

 be readily studied in various stages of development. The testes 

 are not known at present in any Brachiopod except the dioecious 

 Thecidium. The red matter suggested by Hancock as possibly 

 testicular in Lingula has its parallel in yellow matter which is 

 abundant amongst the ovarian ova of Terehratula. This yellow 

 matter is clearly due to degeneration of the envelopes of escaped 

 ova — is, in fact, a series of corpora lutea. 



I think it has not yet been clearly pointed out that the ova 

 in Terehratula do not lie freely on the surface of the body- 

 wall ready to drop into the blood-sinus (perivisceral cavity), 

 into which the oviduct opens. Each ovum has really a very 

 delicate connective-tissue envelope ; and it is only upon bursting 

 through that that it can escape. Sometimes the ovaries (in De- 

 cember) contain comparatively large eggs, which are readily 

 detached. In the spring, on the other hand, I found most with 

 moderate-sized ova, but some with no ova at all. The ovarian 



