366 CARL VOGT. 



cuticle and a layer of hypodermic cells. To these must be added, 

 in the interior, the tissue of the intestine itself (the endoderm) 

 of an obscurely cellular structure. 



The ah mentary canal (iV) has the form of a long-necked flask, but 

 is liable to variation according to the degree in which it is con- 

 tracted. It terminates below in a large, rounded cul de-sac, 

 which is often much dilated. When in this condition, the author 

 has noticed two dark parallel lines, enclosing a lighter longitu- 

 dinal space, which originates at the base of the cul-de-sac, and 

 ascends with a sHght curve towards the buccal aperture. This 

 is, no doubt, the rudimentary state of tlie intestine proper, and a 

 %xii2iSS. papilla at its upper extremity marks the future position of 

 the anal orifice, so that the plan of the alimentary system is 

 already in the larva conformed to the type of the adult animal. 

 At the same time it is undoubted that the cul-de-sac (stomach) is 

 completely closed below, and is absolutely separated from the 

 hypodermic layer. 



The ciliary crown or wreath (m). — This is a large circular 

 organ which can be expanded or drawn over the buccal promi- 

 nence like a hood. It is sometimes inflated, and sometimes con- 

 tracted so as to resemble in form the vela of the Gasteropod 

 embryo, a resemblance that is increased when the buccal mammilla 

 is wholly withdrawn, leaving a depression lined with cilia, which 

 appears to divide the crown into two lateral expansions. The 

 cilia on the wreath are long and stout, and are connected with 

 large granular cells which are clearly developed from the hypo- 

 dermic layer.^ 



The eye-speclcs (6') make their appearance at an early stage of 

 the development, while the embryo is still enclosed in the 

 ovum. They are of a yellowish-red colour, situated inside the 

 hypodermic layer, and seem to be nothing more than pig- 

 ment masses. Neither nerves nor refractive corpuscles could be 

 detected.^ 



The spectacle organ (r) is composed of two circular hollows 

 surrounded by a thick border made up of cuticle and hypodermic 

 cells, which forms a kind of bridge between the hollows. At the 

 bottom of each depression are five or six conical papilla sup- 

 porting long and broad cilia, which can be pushed forth or 

 withdrawn to the bottom of the hollow. 



The caudal appendage (t) is situated in the centre of the 



^ The embryo of Pedicellina closely resembles that of Loxosoma in this 

 portion of its structure. It is furnished with a kind of contractile mantle, 

 which cau be folded over the anterior surface of its body or turned outwards, 

 so as to form a ciliated locomotive organ. — Transl. 



^ In the embryo of the Cheilostomatous genus Biigida, Nitsche has de- 

 scribed eye-specks furnished with a retractile corpuscle. In some cases as 

 many as ten were present on a single individual. — Transl. 



