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THE AMERICAN NATURALIST [Vol. XLI 



of Ann Arbor, and a single example was taken on April 9, in a 

 field several hundred yards distant from the nearest pond where 

 spermatophores were found ; but the eggs of the two species are 

 easily distinguishable, and in the case of A. pundatum were iden- 

 tified by means of eggs laid in the laboratory. With the exception 

 of one bunch of eggs of A. tigrinum, all the eggs found in the pond 

 where spermatophores were observed, were those of A. pundatum. 

 With the single exception above noted, the two species have not 

 been known to breed in the same ponds in the vicinity of Ann 



B. The Spermatozoa. The spermatozoon of Amhlystoma punc- 

 tatum is extremely long and slender. The head stains well with 

 Delafields' haemotoxylin, the middle-piece less deeply. The tail- 

 piece is bordered on one side by a very delicate undulating mem- 

 brane. Some of the dimensions are as follows: 



Length of acrosome 20 /x 



"head 106 



" " middle-piece 14 /x 



" tail-piece 480 /x 



Total length 620 // 



The spermatozoon resembles in size and form that of Triton 

 viridescens, with which it was compared, but the latter has a 

 middle-piece twice as long, and a more conspicuous undulating 



As compared with the spermatozoon of Crytohranchus allcr/hr- 

 niensis (Smith '06) the sperm of Amhlij.stoma pundatum is nearly 

 three times as long, with a proportionally much longer middle- 

 piece; the entire structure is much more slender and thread-like. 



In freshly mounted seminal fluid the spermatozoa were seen in 

 active motion. They tend to cling together parallel to each other 

 to form bundles or ringlets, revolving with a circular motion; 

 when so clustered tliey retain their vitality much longer than when 



It -nHhially hwumv, .l..uer until with a InVI, nia-nification it is 



if form across the entire fi.'M <.f the niicn.sc.pc. Tl^. un.lulatino- 

 membrane <loes not wind alx.ut the >liaft as in ('ryi.t..l)ran<hus, 

 but continues on one side of it. When dead, the sperms are usually 



