4o8 



DISCOVERY REPORTS 



mammalian testis the material should be fixed within a very few minutes of death. In 

 the case of whales, one is fortunate if the tissue has been dead less than three or four 

 hours. However, surprisingly good fixation can sometimes be achieved and, the nuclei 

 being very large, even some cytological observations can be made. 



The mature testis can of course be distinguished at a glance from the immature. 

 The tubules are much larger and may be filled with nuclei in various degrees of 

 abundance. In some cases the lumen is packed with a dense mass of cells, and in 

 others the latter may be loosely scattered, or clustered only round the rim of the 

 tubule, leaving an empty space in the middle. In extreme cases the tubule appears to 

 be practically empty. It is difficult to say whether these spaces are in part due to bad 

 preservation, but in the testis of No. 114 (Fin), in which the fixation was probably 

 better than in any other, the tubules showed large spaces (Fig. 141). 



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Fig. 141. Section of normal testis of an adult Fin whale. 



Germ cells may be seen in various stages of development, but it is difficult to follow 

 out much of the process of spermatogenesis. Figs. 142 and 143 illustrate some 

 of the stages most commonly seen. (Both are from the same specimen as Fig. 141 .) 

 Among all the testes, of which sections have been cut, the conditions are found to vary 

 at different times of year. In the majority of cases spermatozoa are present in very 

 small numbers. They appear to be produced all the year round, but only in very small 

 quantities, except at one particular season. Sections have been prepared from whales 

 killed in ever)' month except June, and it is found that in April and May, and in the 

 case of one whale in July, the testis assumes a different histological appearance from 

 that of whales killed in other months. The difference is noticeable partly in the relative 

 abundance of spermatozoa throughout the tubules, but mostly in the enormous 

 quantity of nuclei which appear in the tubules. In other months the tubules show 



