ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 231 



margins of the lobes ; by tliis arrangement the point of origin of the 

 sensory nerves thence given off is somewhat increased in extent. 



The brain of Gunda ulae differs in some points from that of C. seg- 

 mentata. Thus, it has three, not four, sensory nerves on either side, 

 and the optic nerve is the most delicate of all ; the minute structure of 

 the brain of this worm is described in some detail. The greater part 

 of the longitudinal nerves take part in forming the brain, but a small 

 ventral portion is continued further forwards, and is separated from the 

 base of the brain by a space beset with ganglionic cells, and there is 

 thus formed the nerve which is ordinarily spoken of as the anterior 

 longitudinal nerve ; this is the chief point in which the brain of Gunda 

 differs from that of other fresh-water Triclades with bilobed brains, for 

 in them the hinder longitudinal nerve-trunk completely fuses with the 

 base of the brain. 



5. Incer^ae Sedis. 



Floscularia annulata.* — Mr. J. Hood describes a new species of 

 Floscularia which he has found in Fifeshire and Perthshire. The corona 

 is a hemispherical cup, the edge of which is cut into three lobes of 

 unequal size ; these not only differ in form from those of F. hoodii and 

 F. trilobata, but also in the fact that the tips of the lobes only are 

 crowned with short seta?, whereas in the other two species there are 

 double rows of setae running round the whole margin of the corona. 

 Examined as a transparent object, F. annulata appeai-s to have three 

 brown rings below the corona ; seen as an opaque object, these are white. 

 The jaws at the entrance to the stomach have an upward motion, and 

 at the same time they open out to seize the food and drag it into the 

 stomach. Sometimes the jaws close on the spherical body of a monad 

 a little below its centre, and " when it so happens that the jaws fail to 

 clutch it, the spherical body rebounds back into the cup, just as a person 

 grasping at an indiarubber ball with finger and thumb just below the 

 centre produces the same result. This rebound shows the toughness 

 and elasticity of the cuticula of these minute monads." Full-grown 

 specimens of F. annulata, the female of which is alone known as yet, 

 are from 1/64 to 1/50 in. in length. 



Nervous System of Myzostoma.f — Dr. F. Nansen gives an account 

 of the anatomy and histology of the nervous system of several species 

 of Myzostoma, and concludes with some generalizations which are more 

 fully treated of in his report to the Bergen Museum. 



The central nervous system of Myzostoma consists of an oesophageal 

 ring, with which ganglia or ganglionic cell-masses are connected, and a 

 short ventral cord with no distinct ventral ganglia, but with indications 

 of segmentation ; in connection with the ring there is a spirally developed 

 complex of nerves in the proboscis, which has never before been detected 

 by any observer. From the oesophageal ring these nerves pass forwards 

 on either side towards the tip of the proboscis, and connect the ring with 

 another — the tentacular nerve-ring, which, though variously developed 

 in different species, has always considerable dimensions ; it is sur- 

 rounded by a thin sheath, within which there are no ganglionic cells ; in 

 M. Graffi, however, the ring is surrounded by a number of cells, which 



* Science-Gossip, 1S8S, pp. 8-10. 



f Jenaisch. Zeitschr. f. Naturwiss., xxi. (1S87) pp. 267-321 (1 pi.). 



