Geoffrey Smith and Mrs Haig Thomas 41 



the hybrid pigeons (Fig. 3, Plate I). The typical appearance of the 

 testicular tubes is shown in Fig. 3, Plate I, and it will be seen that 

 after the spireme stage of the primary spermatocytes, the cells appear 

 to have fragmented irregularly, and the chromatin in them appears as 

 intensely staining irregular masses which assume branching and beaded 

 threads. These degenerate fragments represent the abnormally shaped 

 spermatozoa which make up the greater number of the spermatozoa 

 found in the vesiculae seminales, and the method of their formation 

 appears to have consisted in a fragmentation of the spermatocytes after 

 the abortive initiation of the reducing division. 



The occurrence in the vesiculae of a certain number of normally 



shaped spermatozoa, though mostly of abnormal size, would seem to 



indicate that a certain number of the primary spermatocytes did divide 



in a less degenerate manner earlier in the year, but I cannot find any 



-evidence of this occurring in the sections. 



It will be seen from this account that degeneration sets in just at 

 the time when the synaptic pairing of the chromosomes should follow 

 the formation of the spireme in the primary spermatocytes, and this 

 agrees with the account given for the hybrid pigeons, except that the 

 degenerative process sets in rather earlier in the case of the hybrid 

 pheasants. This earlier degeneration in the latter case accounts for 

 the far greater proportion of deformed spermatozoa found in the 

 pheasant compared to the pigeon. Besides the two sterile males, three 

 sterile females from the same crosses, viz. two produced by Reeve's 

 $ X Formosan </ and one by Reeve's ? x versicolor- </", were dissected. 

 The Reeve's x Formosan hybrids were rather over two years old, and 

 had never laid eggs ; the Reeve's x versicolor female was three years 

 old and had likewise never laid. 



The 'Reeve s X versicolor female (M) did not show any marked 

 assumption of male characters in the plumage, except in the pattern 

 of the interscapulars which showed a trace of the male Reeve's type. 

 There was a very small ovary which however contained some fair-sized 

 oocytes, and the oviduct was small and undeveloped. Unfortunately 

 the ovary of this bird was lost, so that no report can be made on its 

 histological structure. Of the two Reeve's x Formosan females, one, 

 which will be referred to as B. showed very slight assumption of 

 Reeve's male pattern in the interscapulars. The ovary consisted of 

 two nodules of tissue about 5 mm. in length, highly vascularised 

 and of a dark red colour. Sections of these nodules showed no trace of 

 oocytes, the whole of the tissue consisting of nests of interstitial cells, 



