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loped spermatozoa, which lie here together in large clusters or heaps (see fig. 23). The 

 single spermatozoa consist (fig. 24) of two sharply distinguished parts, head and tail. The 

 head is more or less globular, completely pellucid, and contains one or more clear nuclei. 

 The so-called tail, which can often attain a very considerable length, has the form of an 

 extremely fine thread or bristle. I could not discover any independent undulating movement 

 in them. But there was during the dissection an evident constant movement of the whole 

 mass of semen, probably caused by the elastic tails or bristles of the spermatozoa gradually 

 straightening themselves out from their original convolved position. 



