ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 171 



molluscs Cardium edule. Purpura JapiUus, and Patella vulgata. An 

 interesting fact regarding the Cardium. parasite is that the cercarise 

 encyst within the sporocyst. They possess a tail, although under these 

 circumstances this organ must he quite useless. The cercaria of Purpura 

 is very contractile, and when moving uses its body more than its tail, 

 shortening and elongating itself continually. 



Structure and Development of Redise.* — E. Eossbach has studied 

 the rediffi in Paludina {Cercaria echinata, adult in ducks, etc.) and 

 Lymiueus {Cercaria armata, adult in frogs), and gives a full account of 

 their structure. He also describes their development, with particular 

 reference to the pharynx, body-cavity, excretory vessels, and terminal 

 •cells. 



Incertse Sedis. 



Budding", Degeneration, and Regeneration in some Marine Ecto- 

 procta.f — 0. Romer has studied Alcijonidium mytili and BuguJa avicu- 

 laria. Jn the formation of the polypid-bud the ectoderm and mesoderm 

 of the zooecium take part. The mesodermic elements of the daughter- 

 zooecium arise from the mesenchyme cells of the mother-zooecium, as well 

 as from proliferating cells of the ectoderm of the daughter-zooecium. 

 The processes of degeneration and phagocytosis are closely similar to 

 those which occur in the degeneration of Ascidian and in the meta- 

 morphosis of Muscid larva. The regenerating polypid is formed like 

 the first polypid-bud, by an invagination of tiie ectoderm with co- 

 operation of the mesoderm, as Seeliger observed in Entoprocta. It is 

 remarkable that old, extremely delicate ectodermic epithelia, poor in 

 protoplasm, should have the capacity of re-exhibiting complete embryonic 

 capacity. They become rich in protoplasm, acquire cylindrical form, 

 return to the blastula condition, show gastrular invagination, and form 

 a new polypid with the most varied tissues. 



Affinities of Hislopia.| — Nelson Annandale discusses Carter's 

 genus ffislopia, and comes to the conclusion that it is a somewhat 

 abeiTant representative of the Ctenostomata, the orifice of the zooecium 

 having undergone special modification, possibly in connection with life 

 in fresh-water. Probably the genus should be regarded as constituting 

 a distinct family closely allied to the Paludicellidse. 



New Species of Myzostoma.§ — August Reichensperger describes 

 31. vincentinum sp. n., from Pentacrinus decorus. Its position seems to 

 be near M. coronatum Graff. 



Rotifera. 



Sex-determination in Hydatina.|| — R. C. Punnett, as a result of 

 breeding many generations of this Rotifer, comes to the conclusion that 

 Maupas' theory that sex in Hydatina is determined by temperature, as 

 well as Nussbaum's idea that it is determined by good or bad nutrition, 



* Zeitschr. wiss. Zool., Ixxxiv. (1906) pp. 361-445 (3 pis.). 



t Tom. cit., pp. 446-78 (2 pis.). 



X Bull. Mus. Comp. Zool. Harvard, xliii. (1906) pp. 199-201 (5 figs.). 



§ Journ. Asiatic Soc. Bengal, ii. (1906) pp. 59-63 (2 figs.). 



H Proc. Rov. Soc, Series B, Ixxviii. (1906) pp. 223-31. 



