162 SUMMARY OF CURRENT RESEARCHES RELATING TO 



mesoderm cells bounding the spaces. There is no genetic connection 

 between the coelothel and the vascular walls. The arterial heart arises 

 from paired primordia which unite in the middle line. Paired clefts in 

 the " mesoderm " form the pericardial primordia, which meet in the 

 middle line. About the same time the kidneys arise from the mesoderm 

 as two distinct solid primordia, which are from the first in close relation 

 with the venas cava?. The ccelomic system consists of the paired renal 

 cavities and the pericardial cavity, which are connected both as regards 

 cavities and epithelial lining. Naef emphasizes three points : that there 

 is no primary connection between kidney and pericardium ; that the peri- 

 cardium has never any direct connection with the exterior ; and that the 

 primordium of the heart has no connection with a sinus of the hind-gut ; 

 indeed this sinus, which Distaso described, is the primordium of the 

 genital veins. 



Catalogue of Recent Cephalopods.* — W. E. Hoyle brings his list 

 of cuttlefishes up to 1906 ; this second supplement dealing with the 

 period 1897-1906, and recording 69 new specific names and 29 new 

 genera, 10 of which, however, are divisions or re-namings of older genera. 



/3. Gastropoda. 



Revision of Chiton s.f — Job. Thiele completes his revision of the 

 order Placophora, and indicates his view of the relationship of the 

 families and sub-families in the following schema : — 



Acanthopleurinse Cryptoplax 



I I 



Sclerochiton Chonepla.r 



I I 



Chitonins* Ischnochitonirue Ghsetopleurinse MopaliicUe Acanthochitinae 



Callochitoninse — Nuttalochiton 



Trachyderrnoninse 



.1 

 Hernial' thrum 



Lepidopleuridse 



Eyes of Placophora. :{: — M. Nowikoff has studied the intra-pigmental 

 eyes of Chiton and Gallochiton, comparing them with the other types of 

 eye that occur. There are two types of intra-pigmental eye, for that of 

 Chitoninse is different from that in Callochitoninas, and both are differ- 

 ent from the extra-pigmental eyes in Toniciinas and the rather more 

 complex forms in Liolophurinae. Yet all the three types seem to be 

 derivable from one and the same material, the cells of the megalassthete. 

 The eyes do not seem capable of more than distinguishing between 

 light and shade, and probably help the animals to keep away from 

 muddy water. 



* Proc. Roy. Pliys. Soc, xvii. (1909) pp. 254-99. 

 t Zoologica, xxii. (1910) Heft 56, pp. 71-124 (4 pis.). 

 j Zeitschr. wiss. Zool., xxxix. (1909) pp. 668-80 (1 pi. and 2 figs.). 



?3 



