ZOOLOGY AND BOTANY, MICEOSCOPYj ETC. ' 101 



primitively free right edge came to lie in a cavity whicli it divides into 

 two. The septum, therefore, which separates the peristomial cavity from 

 the septal space is nothing more than the hindermost part of the primi- 

 tively right peristomial margin, which by a special process of growth has 

 become inclosed in the interior of the body. This history explains the 

 presence of cilia on it. 



With regard to the finer structural relations of this cell, the author 

 compares the endoplasm to that of Noctiluca miliaris, for in both the large 

 protoplasmic strands exhibit a fine plexiform structure. The ectoplasm is 

 not of the ordinary type, but the outer layer is specially differentiated, 

 and ought to be distinguished from what is seen in Ehizopods and many 

 Infusoria. Attention is directed to its radiate structure, and it is shown 

 that this has nothing to do with the presence of cilia. It is observed that 

 in all the striations of the peristome the separate bands are connected with 

 one another by transverse bars of protoplasm, which appear to lie deep. 

 In prepared specimens it is possible to see on either side of a peristomial 

 band a series of fine dots ; if the focus be altered we get an optic section of 

 a membranella, which is not simple, but is composed of two more or less 

 approximated lines ; if the focus be again altered, the fibrillated margin of 

 the membranella may be seen. The fine dots appear to be the sections 

 of the fine bands, and these perhaps are to be regarded as the primitive 

 elements of the membranellse. Further observations are necessary to 

 determine whether we may regard the membranellsB of Bursaria as being 

 made up of two rows of cilia. The transverse bands seen in the peristome 

 are the points of attachment of the membranellas. 



Morphologically, the peristomial and the connected transverse bands 

 are nothing more than specially thickened parts of the ectoplasm, which 

 appear to owe their origin to the connection with the system of stria9 in the 

 peristome ; so far as the author knows, nothing like them has been found in 

 any other infusorian, and their function still remains to be discovered. 



Food Habit of Petalomonas.* — Dr. A. C. Stokes believes that the 

 flagellum in Petalomonas carinata arises from the bottom of the deep oral 

 aperture. The animal feeds on bacilli and spirilla ; when in the neighbour- 

 hood of masses of these bacteria, it comes to rest ; the flagellum, with the 

 exception of the free end, is motionless. The bacteria, either by their own 

 movement, or by that of the free-end of the flagellum, knock against the 

 motionless portion, and glide down into the oral aperture. From this they 

 may escape, unless they touch the slightly oblique posterior wall of the 

 oral pit when they are engulfed in the protoplasm. The bacteria are 

 frequently seen to return again and again to the pit after their escape. 



The author asks "What is the special attraction that leads them to 

 congregate in the pit, and why should the bacteria allow themselves to be 

 thus engulfed ? " The latter probably is due to the oblique plane at the 

 bottom of the pit. 



Gymnodinium polyphemus.-f — The specific name is given to this 

 flagellate protozoon by M. Pouchet, from the fact that it possesses an eye 

 of considerable complexity. 



The eye consists of a transparent, highly refracting lens, rounded at its 

 free extremity, which is always directed forwards. The inner surface is 

 imbedded in a hemispherical cap-like mass of pigment, which represents 

 a choroid. In some of the forms this pigment is red, in others black. In 

 young forms, even when still encysted or undergoing fission, this lens is 



* Sci.-Gossip, 1886, pp. 273-4 (1 fig.). t Comptes Eendus, ciii. (1886) pp. 801-3. 



