ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 03 



of touch, and is well provided with nerves. The tip of the wheel-organ 

 is not a syncytium, but is composed of several parts. The pharynx is 

 spherical, and surrounded by five large ventral, and several smaller 

 lateral salivary glands. These salivary glands are connected with the 

 oesophagus. 



The two excretory tubes open into the rectum without any contractile 

 vesicle ; no ciliated infundibula were observed. The eggs develope in the 

 coelom. 



The author believes that the bilobed wheel-organ of the Philodinida? 

 may be referred to the ciliary circlet of the trochosphere, that the 

 proboscis is the homologue of the anterior end and a part of the frontal 

 plate of the trochophore, and that the brain of Eotifers is partly formed 

 by the frontal plate, and partly by the connection with it of primitively 

 peripheral ganglion cells. 



Echinodermata. 



Histology of Echinoderms.* — Dr. 0. Hamann deals in this essay 

 with the regular Echinoidea and Spatangida. He accepts Valentin's 

 fourfold classification of the pedicellaria?, which he calls gemmiformes, 

 tridactyli, ophiocephali, and trifoliata?. The first of these are described 

 in Sphsereclunus granulans and Echinus acutus. A careful description is 

 given of their musculature and nerve-supply. The glands which are 

 found on the stalks agree in structure with the globifera?, and, as in 

 them, stimulation produces a flow of finely granular mucus, which coagu- 

 lates at once in either water or alcohol. The gland-cells are irregular, 

 and their oval nuclei are surrounded by only a small quantity of cell- 

 substance. Below the basal membrane there is a layer of concentrically 

 disposed smooth muscular fibres, by the contraction of which the secre- 

 tion is evacuated. The connective substance in which the glands are 

 imbedded is very poorly developed. The orifice of the gland is dorsal 

 to the calcareous tip of the pedicellaria. 



The tridactyle pedicellaria?, which were found in all the Echinids 

 examined, are described in Centrostephanus longispinus and Dorocidaris 

 papilla ta. In the latter, one form is remarkable for the possession of 

 glandular tubes on the branches. These tubes are quite different in 

 form from those of the gemma?forni pedicellaria?. A few short tubes 

 hang together in a racemose fashion, and open into a long efferent duct ; 

 they are set in the connective tissue, and their epithelium consists of 

 finely granular flattened cells, which pour their secretion into the narrow 

 lumen of each tube. These peculiar pedicellaria? are principally to be 

 found on the oral membrane. The buccal pedicellaria? are the simplest 

 of the trifoliate type, having neither glands nor special sensory organs. 



In discussing the mechanism of the movements of the mobile termina- 

 tions of the pedicellaria?, investigators appear to have confined their 

 attention to the three adductor muscles, and have been content to explain 

 the separation of the arms by the elasticity of the parts. Dr. Hamann 

 has discovered extensor muscles which are inserted into the same 

 calcareous pieces as the adductors, but on the outer surface, and nearer 

 the base of the calcareous plates. As to the functions of these organs, 

 which have been so much discussed, it appears to be necessary to distin- 

 guish between the various kinds. Their numerous nerve-endings seem 



* Jenaisch. Ztitschr. f. Natunviss., xxi. (1887) pp. 87-2G6 (13 pis.). 



