Hoiv to p-e])are Specimens of Diatomacese. 225 



I will also add here that careful examination of the guinea- 

 worm [F. medinensis) has led me to conclude that in this congener 

 worm also the intestine terminates in an anal oritice a little within 

 the concavity of the curled tail, and so in this anatomical point the 

 worms are in unison. 



Merging of the two Uterine Channels or Horns into one common 

 Tube. — It is quite clear that this is incorrect. The two canals, 

 diverging from the vagina, do not coalesce, but continue separate 

 throughout, though placed in close apposition and hound one to the 

 other by numerous fibres. When within a distance of the tail 

 varying from 3 to 1|- inches, each uterine horn merges into an 

 ovarian tube, as detailed at p. 161 and illustrated in Plate XXXI., 

 Fig. 7. The ovarian tube is coiled upon itself, but when extended 

 averages 5 inches in length ; it is continuous from one uterine horn 

 to the other, and varies in diameter from o-ioth inch at its junction 

 with the uterine channels to xio^th inch midway, becoming again 

 reduced to the smaller measurement at the extreme loop. The 

 remarkably close binding of the one horn of the uterus to the 

 other in their course from the vagina to the ovarian tube, and 

 the difficulty of unravelling them without tearing their delicate walls 

 and so obscuring accuracy of observation, led me to regard these 

 tubes as one, but the tracing of the ovarian coils upwards has ren- 

 dered clear these amended details of the generative system. 



With these modifications I believe that the anatomy of the 

 Filaria immitis, as detailed in my former paper, is substantially 

 correct. 



V. — How to prepare Specimens of Diatomacese for Examination 

 and Study hy means of the Microscope. 



By A. Mead Edwards, M.D., Newark, New Jersey, U.S. 



[The Author having kindly forwarded to us early proofs of the following 

 article, we have much pleasure in giving it insertion.] 



Having accumulated a number of gatherings of rough material, 

 which, a cursory examination has shown, contain specimens of 

 Diatomacese, and which, it is judged, it will answer to clean and 

 otherwise arrange and put up, or, as it is technically termed, 

 " mount, " for future study, the intending diatomist requires to be 

 informed how he may best set about preparing his specimens in the 

 most advantageous manner. The author of the present sketch has 

 published, in the seventh volume of the ' Proceedings of the Boston 

 (Mass.) Society of Natural History,' certain directions for collecting, 

 preparing, and mounting Diatomacese for the microscope ; and as 

 that paper contains a large part of the information he desires to 



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