150 



and I am inclined to consider them also as spermatophors ; 

 identical thus in their nature with the Pachydermon of 

 Claparede. In the spermatic reservoirs of Nais serpentina 

 were also a few floating spermatozoa and very remarkable 

 flat rhombic crystals of small size, which disappeared on the 

 addition of weak acetic acid. If this interpretation of Pachy- 

 dermon and of the coiling filaments of the spermatic reser- 

 voirs of Nais be correct, we may state, as a new and not 

 unimportant fact, that spermatophors are developed in the 

 following genera of oligochacta, viz. Clitellio, Tubifex, Limno- 

 driluSf Nais, and Stylaria. 



References. Opalmcc. 



SchuUze. — Beitrage zur Naiurgescb. der Turbellaiien. 



Greifswald, 1851. 



Stein. — Die Infusions tliiere auf ilireEntwickelungsges- 



chichte untersucht. Leipzig, 1854. P. 181. 



Stein. — Der Organisnms der Infusions thiere. Iste 



Abtheilung, 1 vol. folio. Leipzig, 1859. P. 91. 



Claparede et Lachmann. — Recherches sur les Infusoires. 



Geneva. 

 Claparede. — Rechercbes sur les Annelides, Turbellaries, &e. 

 Observes dans les Hebrides. Geneva, 1860. 



Pachydermon. 

 Claparede. — Recberclies sur les Annelides, Turbellaries, &c. 



P. 88. PL IV, fig. 1 and \a. 

 Claparede. — Recbercbes Anatomiques sur les Oligoclietes. 



Geneva, 1862. Plate IV, fig. 12. 

 D'Udekem. — Hist. Nat. du Tubifex rivulorum. Mem. de 



I'Acad. de Belg. Tom. 26. 1855. 

 VUdekem. — (As to Stylaria). Developpement du Lombric 

 terrestre. Mem. de I'Aead. de Belg. Tom. 

 27. 1856. 

 Claparede and Mecznikow. — (Spermatoplior of Spio). Beitrage zur Kentniss 



der Entwick, der Cbastopoden. Zeitsclu". 

 fur wiss. Zoologie. Bd. XIX. 



On Microscopic Illumination. By John F. Higgins, 

 A.M., M.D. Read before the American Microscopical 

 Society of the City of New York, October 12th, 1869. 



The subject of illumination in the use of the microscope 

 is one upon which much has been written, especially in con- 

 nection with the merits of various accessories, and yet one 

 the understanding of which is far from general, and, more- 

 over, in reference to which microscopists of acknowledged 



