ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 313 



animal, the most striking characteristic being the pear-shaped terminal 

 appendix, in which the excretory system opens to the exterior by lateral 

 ducts. The ova are not liberated from abstracted joints, but pass out 

 by the female genital aperture, and are included in the frecal balls of the 

 host. 



Monozoic Nature of Cestoda.* — J. W. Spengel discusses the descent 

 of the Cestodes and the question of their individuality. They are single 

 animals. Some of his proofs may be quoted. There are cerebral ganglia 

 in the scolex ; in the proglottides corresponding central organs are absent. 

 All metazoa which form colonies have in a great degree the power of 

 regeneration ; this has never been observed in Cestoda, while its 

 absence is proved by the frequently described "fenestras," or perfora- 

 tions occurring in very young segments. The formation of proglottides 

 is regarded as originally independent of the segmentation of the sexual 

 apparatus — both coincide only in the higher Cestodes. They owe their 

 origin to the locomotor activity of the free hinder border of the original 

 proglottis. The distinct independence of separated segments in many 

 Cestodes, e.g. Gall lob othrium, has no special bearing on the monozoic 

 view, since analogous cases exist in other animals, e.g. Comatulidas, 

 Autolytus, and the " Palolo worm." 



Distribution and Geological Age of Genus Oochoristica Liihe.t — 

 F. Zschokke describes a new species of 0. rostellata from Zamenis 

 viridiflavus. The genus has an extremely wide geographical distribu- 

 tion, as well as very great variety in the matter of principal hosts. These 

 facts bespeak a great geological age. In favour of this view is the fact 

 that the South American hosts are exclusively ancient types ; the parasites 

 are not found in the animals which immigrated from North to South 

 America at the Pliocene period, and they probably infested South 

 American Mammalia in Tertiary times. 



Trematodes of Bivalves.:}: — W. Nicoll describes various parasites, 

 viz. Cercarige from Cardinal, which do not occur in the same situation as 

 those discovered by Jameson ; an encysted Trematode larva from the 

 mantle edge, the adult of which occurs in the oyster-catches (ffcema- 

 topus ostralegus). It belongs to the sub-genus Echinostomum, and is 

 probably a new species. The same parasite was found also in Mytilus 

 and Mactra. Ciliated sporocysts were also found in Cardium in the liver 

 and other situations, but no relation to the Cercarias present in the same 

 host has been made out. 



Excretory System in Fresh-water Triclads.§ — J. Wilhelmi has 

 investigated and describes in detail the conditions of this system in five 

 species. There are dorsally, right and left, two main stems, which branch 

 greatly and again unite. Branchings over the whole dorsal region, as 

 described by Chichkoff in Dendrocailum, are not present in that species, 

 nor are the transverse anastomoses which he described. In general 

 the system resembles that of Cestodes and Trematodes in essentials, and 



* Zeitschr. wiss. Zool., lxxxii. (1905) pp. 252-87. 



t Op. cit., lxxxiii. (1905) pp. 53-67 (1 pi.). 



+ Ann. Nat. Hist., xcvii. (1906) pp. 148-55 (1 pi.). 



5 Zeitschr. wiss. Zool. lxxx. (1906) pp. 544-75 (2 pis.). 



