MR 



E. R. LANKESTER ON SOME LOWER ANNELIDS. \ 



commences, in each of which there are eight booklets starter than the cephalic, l.ut 

 similar in all other respects. An individual seems sometime to have seven or .i u hi „f 

 these "abdominal bristle-bundles," as they may be called, in distinction lion, the 

 "cephalic bristle-bundles;" but this is not really the . tse, as the study of ih d volo] 

 ment of the zooids shows that the posterior four belong to a lie* aooid. Pour abdomin 



bristle-bundles are all an individual possesses; how many segments are indi ai. I 1 

 these and the cephalic bundles is questionable. The muscles and bit e^u rami at the 

 insertion of each abdominal bristle-bundle form an elevation on the surface < i the bod 

 comparable to a foot in the Polychteta, and give this species of C/t, faster, when i h \ 

 in action, a curious resemblance to some Tardigrada. The brisil. .bundles are used 

 simply for locomotion, and each can be spread out like a fan or turned so as to point the 

 reflected apices in any direction. The cephalic bristle-bundles are not used I r pre- 

 hension of food (which is effected by the rapid and powerful intermittent sucking- action 

 of the pharynx), but perform the same part in locomotion as the anterior sucker of a 

 leech or the anterior feet of a caterpillar. The form and number of the bristles, and tin 

 general proportions of the body, are the points which give the best specific ehai eter in 

 Chcetogaster. 



Common Characters of the Tissues*. — Chatogaster Hmutei is almost perfectly coiotirle^ 

 and transparent, the only colour developed in its body being in a few brownish ranules 

 surrounding the alimentary canal, which often also contains coloured mailer. This dors 

 not render the observation of its organs and structure at all easy, lift there SJ u< 

 contrasting tints to guide the eye. At the same time the density of its various ti in- 



appears to be very equal, and little more than that of the surrounding water. This 



condition of things, which is found in Infusoria and many low Turbellarians, is connected 

 with the fact that when they are crushed and water admitted freely to mix with th 

 tissues, they rapidly swell up, dissolve, and almost entirely disappear. This being th 

 case with Chcetogaster limncei renders any dissection of it impossible. It may be ft t- 



tened to a certain extent by pressure; but when the creature is once burst, it soon 



becomes a mass of floating cells and vesicles, many of which ai evidently produced by 



the action of the water. In the living Chcctog«ster the histological e] ments to b, 



distinguished are— homogeneous substance, granules, iibrillated substance, hexagonal, 



b ^xoxxv^. c*xv, A .w.^w 



compressed, and floating globular cells. „ . 



The Integument.-^ the use of weak acetic acid a superficial structure (« matnx of 



Levdig), consisting of small closely fitted hexagonal cells with roonded nuclei and nucleoli, 



is rendered very evident in the integument of the worm (Plate XLIV fig. 3- . Ai ry 

 delicate « cuticle" is all that lies externally to these edk ; and filamentous prolongation, 

 of the substance of the cells are very abundant on some parts ot the body, 

 towards the anterior region and on the lip. They are similar to ha.r-l.ke pro, s 

 Nais, in Sagitta, in young Annelida, and the Xurbellaria generally, su.-l, as . StoettuU 

 Wright has proposed to call - palpoeils." In this tessellated by, are d.sposed n t , a 

 lar g : clear oval bodies, which are so numerous and large, in som< peennens, , to produ, 



These r en,a rk8 appfy to the i— e, ase.ua. condition. Important histoh*. 1 change, go on when fe ,n,- 



talia are developed. 





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