764 JOHN BEARD, The determination of sex in animal development. 



Description of Plate. 



Plate 4 5. 



Fig. 1. The two forms of spei'inatozoa, the hairlike and the giant- 

 sperm, of man {Homo sapiens). After von Wideuspeug, from Waldever, 

 'Die Geschlechtszellen', in : Hertwig's Handbuch der vergleichenden und 

 experimentellen Entwicklungslehre der Wirbelthiere. 1000 : 1. 



Fig. 2. The two forms of spermatozoa of Hyla arborea. After 

 VON La Valette St. George. From the same source as Fig. 4. 



Fig. 8. Three stages in the spermatogenesis of the wormlike sperm 

 of Paludina vivipara. After F. Meves. From Korschelt & Heider, 

 Lehrbuch der vergleichenden Entwicklungsgeschichte der wirbellosen 

 Thiere, Allgemeiner Theil, 1902. 



Fig. 4. A the wormlike, and B the hairlike spermatozoa of Palu- 

 dina vivipara, and C the two ends of the former under high magni- 

 fication. After F. Meves. From Korschelt & Heider as before. 



Fig. 5. Wormlike spermatozoa, A of Cypraea caput serpentis, B 

 and C of Murex brandaris (B unripe, und C completely formed), D of 

 Pteroceras lamhis, E of Stromhus lentiginosus, and F hairlike or ordinary 

 sperm of the latter species. B and C after R. Koehler, the rest after 

 Brock. From Korschelt & Heider as before. 



Fig. 6. Cocoon of Dinophilus apatris = gprociliatus, with large 

 female- and small male-eggs. After Korschelt. From Korschelt & 

 Heider as before. 



Fig. 7. The life-cycle of Phylloxera vastatrix after Leuckart 

 & NiTSOHE and after Ritter & Rübsamen, from Wbismann, Descendenz- 

 theorie, 1902. The figure is reproduced to illustrate the female-, J5J^, 

 and the male-, E^^ eggs. JP' and F'^ are respectively the female and 

 male forms arising from these. 



Krnmniannsche Buchdruckerei (Hermann Pohle) in Jena. — 2360 



