ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 17 



of others (e.g. Chromodoridae among Nudibranch Molluscs, and 

 Pseudoceridje among Planarians), may be features indicative of a sub- 

 tropical fauna, or indications of a different balance of life obtaining in 

 the two oceans. Crossland has a good deal to say about the various 

 animals which help to form the organic rocks of the shore. 



Tunicata. 



Structure of Appendiculariae.* — W. Salensky gives an account of 

 the structure of Oikopleura rufescens, Fritillaria pellucida, and 

 F. borealis. He discusses in particular the " house," the oikoplasts, the 

 buccal glands, the nervous system and sense-organs, the alimentary 

 tract, the cardiac structures, and the gonads. 



INVERTEBRATA. 



Mollusca. 

 a - Cephalopoda. 



Retina of Nautilus and other Cephalopods.f — H. Merton finds 

 that the retina of Nautilus, studied in spirit specimens, is of a somewhat 

 unusual type. It is possible to distinguish a phaesome, a fibril, and a 

 rod portion in connection with the optic cells. The eye of some of the 

 littoral Annelids comes nearest that of Nautilus, which, complicated as it 

 is in its own way, is of a more primitive type than that of the Dibran- 

 chiata. In the Dibranchiata it is not possible to distinguish a special 

 nerve fibril as the receptive organ in the optic cell ; there does not seem 

 to be a terminal knob in connection with the fibril ; the nerve fibre 

 entering proximally into the optic cell can be followed to the level of 

 the rod-socket. 



|8. Gastropoda. 



Protoconch in Gastropods.^ — H. Leighton Kesteven regards the 

 ideal protoconch as including (1) the plug of the primitive shell-gland ; 

 (2) a portion formed by the veliger ; (3) a portion formed during the 

 nepionic stage, and finally (4) a portion formed during early neanic 

 stages. He calls these four component parts phyloconch, veloconch, 

 nepioconch, and ananeanoconch, and he discusses their varied degrees of 

 representation. The naticoid initial whorl and the systematic value of 

 the protoconch are also discussed. 



Genital Organs of Polycera.§ — H. Pohl gives an account of the 

 minute structure of the genital system of Polycera quadrilineata, 

 together with particulars regarding its general topography. The 

 nidamental gland arises through a special differentiation of a simple 

 " Gangschleife," and is thus not (as was formerly believed) a special 

 subsidiary gland of the oviduct. It is like the albumen gland, only a 

 specialised region of it. That the eggs actually pass through the 

 nidamental gland is certain from the shape of the spawn ribbon, which 

 has the form of the pars constricta. There is a long ductus receptaculo 



* Mem. Acad. Imp. Sci. St. Petersbourg, xv. (1904) pp. 1-106 (12 pis.). 



+ Zeitschr. wiss. Zool., lxxix. (1905) pp. 325-96 (3 pis. and 2 figs.). 



% Proc. Linn. Soc. N.S. Wales., xxx. (1905) pp. 325-35 (2 figs.). 



§ Zool. Jahrb. Abt. Anat., xxi. (1905) pp. 427-52 (2 pis.). 



Feb. 21st, 1906 c 



