178 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



genitalia which renders cross-fertilisation between nearly related species 

 difficult or impossible. He comes to the conclusion that structural 

 variation and the isolation which parasitism implies, are not in them- 

 selves sufficient to account for the establishment of new species. There 

 must also be reproductive isolation. 



Dipylidium caninum in Man.* — F. Zschokke reports a case of a 

 four-year old boy who was infected with this common tapeworm (better 

 known as Tcenia cucumerina) of cats and dogs. 0. von Bollinger f 

 reports four cases, two adult women, two children, of the same occur- 

 rence, which he thinks is commoner than is supposed. Altogether 41 

 cases have been put on record. 



Origin of Gonoducts in Platodes.J — A. Luther gives some notes 

 on the question of the relation of the gonoducts to the excretory system. 

 He is of opinion that the gonoducts in Turbellaria have arisen quite 

 independently of the excretory canals, and that since the corresponding 

 organs in Trematodes and Cestodes are undoubtedly derived from those 

 of Turbellaria, this conclusion applies to all Platodes. 



New Distomidse from Chelonians. § — Georg Heymann describes 

 from the small intestine of Dermatemys mavii Gray, Patagium brachy- 

 delphkim g. et sp. n., an immature species of Telorchis, and an undeter- 

 mined immature Distomid. From the same region of Kachuga tectum 

 Gray, are noted Distomum apolaimum sp. n., and an immature Distomum, 

 whose species is undetermined. 



New Distomidse from Rana.||— W. Klein gives an account of four 

 new forms from Rana hexadactyla. The genera represented are Pneu- 

 monoeces, Halipegus, Phurogenes, and Ganeo, g. n. Keys for the 

 diagnoses of species of the genera Pneumonoeces and Plurogenes are 

 included in the paper. 



Incertae Sedis. 



Development of Pedicellina echinata.f — J. Lebedinsky has fol- 

 lowed the development of this Polyzoon. Some of his results may be 

 briefly stated. In the first directive spindle there are eight chromo- 

 somes ; several spermatozoa enter the egg, but only one survives ; the 

 segmentation is total and unequal ; a bipolar blastula results ; a gastrula 

 is formed by invagination ; there are two primary mesoblasts. 



The dorsal organ, or " head-ganglion," is formed by an invagination 

 of ectoderm ; its ciliated cavity communicates with the exterior ; it 

 forms three pairs of commissures. There is a true oesophageal nerve 

 ring. The " cement gland " arises as an invagination of ectoderm, and 

 is indistinctly differentiated into " punktsubstanz " and ganglion-cells. 

 The atrium arises as a ventral invagination ; the vagina is formed as a 



* Centralbl. Bakt. Parasit., xxxviii. (1905) p. 534. 



t Deutsch. Arch. Klin. Med., lxxxiv. (1905) pp. 50-6. See also Zool. Zentralbl., 

 xii. (1905) pp. 567-8. 



% Zool. Anzeig., xxix. (1905) pp. 409-11. 



§ Zool. Jahrb. Abt. Syst., xxii. (1905) pp. 81-100 (1 pi. and 2 figs.). 



|| Tom. cit., pp. 59-80 (1 pi.). 



1 Biol. Centralbl., xxv. (1905) pp. 536-48 (2 figs.). 



