736 JOHN BEARD, 



instances, in Mollusca, Rotifera, Insecta, Amphibia, Aves, and Mam- 

 malia, even in the human subject. 



Regarding their forms and occurrence K. von Bardeleben*) 

 has furnished interesting data for monotremes, marsupials, the hedge- 

 hog, and man himself. Considerations of space preclude further 

 citation from his memoir, but it may be noted, that the author fully 

 recognises the dimorphism, that he compares the two forms of mam- 

 malian spermatozoa with those of Paludina, and that he describes the 

 second form as often rudimentary and always non-functional. More 

 recently a second form of spermatozoon of Bomhinator has been fully 

 described by Ivar Broman ^). 



The subjoined list of instances of dimorphic forms of spermatozoa, 

 already recorded, with the names of the observers, who have noted 

 or described them, may be of interest: 



Mollusca: Paludina vivipara (Figs. 3 and 4, von Siebold, 

 1836, F. Leydig, L. Auerbach, M, von Brunn, R. v. Erlanger, 

 F. Meves), (Fig. 5, P. Köhler, 1892), Murex brandaris (L. Schenk, 

 M. von Brunn). 



And tlie following all by M. von Brunn: ÄmpuUaria (sp.?), 

 Murex trunculus, Cerithium vulgatum, Nassa mutabilis, Fusus syracu- 

 sanus, Murex erinaceus, Columbella rustica, Marsenia (sp. ?), Äporrhais 

 pespelecani^ Cassidaria echinopJiora, Dolium galea, Tritonium cutaceum, 

 Tritonium parthenopeum, Vermetus gigas, Murex trunculus. Cypraea 

 caput-serpentis (Fig. 5 A), Pieroceras lambis (Fig. 5 D), Strombus 

 lentiginosus (Fig. 5 E, J. Brock, 1887), TyphoUas (J, E. S. Moore, 

 1898, in: Quart. J. microsc. Sc, V. 41, p. 192). 



Rotifera: Notommata sieboldi (F. Leydig, 1854). 



Arthropoda: Äsellus aquaticus (W. Zenker), Oniscus murarius? 

 (F. Leydig), Cicada tibicen (E. V. Wilcox), Pygaera bucephala 

 (F. Meves), Staphylinus (Nils Holmgren), PyrrJwcoris (Henking, 

 1891), Änasa (Paulmier, 1899). 



Nemertea: Tetrastemma (Bollies Lee, 1887). 



Amphibia: Various species of Bufo, Hyla (Fig. 2), Bana 

 esculenta (von la Valette St. George), Bombinator igneus (Ivar 

 Broman). 



1) VON Bardeleben, K., Dimorphismus der männlichen Greschlechts- 

 zellen bei Säugetieren, in: Anat. Anz., V. 17, 1897, p. 564 — 569, 6 ügs. 



2) Broman, Ivar, TJeber die Histogenèse der Riesenspermien bei 

 Bombinator, in: Verh. anat. Ges. 1900, (Pavia), p. 157—164, 19 figs. 



