INVERTEBRATA, CRTPTOGAMIA, MICEOSCOPY, ETC. 75 



extreme modification of the flattened vesicle. On the inner surface 

 the cuticle forms strongly projecting and greatly developed costas ; the 

 wall is formed by a thin membrane, and is provided at its base with 

 an irregularly circular ring (this basal ring appears to be lost in 

 all spirit specimens) ; and the nerve supply consists of a number of 

 bundles of nerve-fibrilla?, which pass to the margins of the calceolus. 

 By their structure they appear, as G. 0. Sars has already noted, to be 

 olfactory organs. Although the calceoli may be easily examined in 

 the fresh state, their investigation is aided by placing them for fifteen 

 or thirty minutes in alcohol. 



There still remain for description another set of sensory organs, 

 the function of which is more obscure. Three different kinds of 

 sensory setae have been observed on the anterior margin of the second 

 pair of maxillas, where they are arranged in three rows ; some of the 

 setae are darkly contoured and pinnate ; others have thin walls, are 

 slightly bent, and are open at their tip ; while others have thick 

 walls and are more curved ; the first set have not yet been observed 

 to be connected with nerves, while the second and third are supplied 

 by the maxillary nerve, and the branches are provided with a large 

 number of ganglia ; in each set of setaa the nerve endings diifer in 

 character, and it is possible that the lowest series represent tactile 

 organs, while those in which the set© are open at the tip are gusta- 

 tory organs. 



The digestive tract is described* as being enveloped along its whole 

 length by a layer of the fatty body, having the majority of its muscular 

 fibres arranged transversely in the region of the small intestine, and 

 with a rectal portion which is well supplied by two layers of muscles, 

 the external set transversely, and the internal longitudinally. The 

 epithelium of the small intestine consists of low, thick cells, with darkly 

 granular contents, while further on the cells are high and the contents 

 much finer. The name of cervical gland is given to the caecal diverti- 

 culum which is found posteriorly to the stomach, and it is described as 

 having a very narrow lumen and a thick epithelial investment formed 

 of closely set cells arranged in two layers. The author, after 

 describing the circular muscles of the hepatic tubes, states that the 

 liver-cells form a single layer, the constituents of which are, in 

 G. polonica, cylindrical towards the blind end, and more rounded and 

 less high as they approach the orifice. Non-nucleated vesicles, which 

 were apparently metamorphosed cells, were to bo observed between 

 the liver-cells, and their presence seems to be in correlation with the 

 secretion of bile. The tubular glands at the commencement of the 

 rectum are now called rectal glands ; their structure is described, 

 and they are stated to contain only a clear fluid and no solid contents, 

 so that their homology with the Malpighian vessels (Sars) is on this, 

 as well a^'on other grounds, to be considered doubtful. An unpaired 

 gland — anal gland — which seems to have hitherto escaped observation, 

 is described ; opening just in front of the anus into the intestine, 

 it is placed in the telson, and lias a ratlier thick membrana i>r(>pria. 

 The lumen is compelled, by tlie dillurencc in size of the epithelial 

 * Loc. rit., p. 511. 



