GU 



Mr. W. Ricldell on a 



more posterior sections are the more markedly female. Tlie 

 depth of the sections varies from ,5"7 to 0*3 tnm., corre- 

 sponding to a body-length of somewhere about 5 cm. probabl}-. 

 In spite of the scantiness of the material, these sections 

 present several features of interest. 



We may begin with such a section as that shown in (ig, 1. 

 At the first glance this appears to pass through an ordinary 

 male pouch on either side. Closer examination shows that in 

 no case are both these testes normal. There are always 

 well-marked ova present in some portion of one or both 

 gonads, sometimes clearly visible under even low power, but 

 tjometimes requiring a fairly high power to detect them, as 

 when the ova are small or the section contains little but the 

 nucleus more or less masked by the spermatozoa. Thus the 

 upper border of the left-hand testis in fig. 1 shows a distinct 

 ovum. None such is visible in the testis of the other side 



Fi£r. 1 . 



Fie 



niider this magnification, but examination of its inner border 

 under a higher power reveals their presence (fig. 2). So far 

 as I can determine, these ova, in such a case as the last, are 

 to be looked for near the inner border of the gonad, dorsal to 

 the vessel — that is to say, they occur in the region of the 

 " Nabel " ■'^ or hilum, the original })Iace of attachment of 

 the gonad. 



Other sections show more com])licated conditions. Fig. 3 

 represents a gonad where the main mass of the tissue is still 

 male, but showing clear invasion by ova. In such a case as 

 this the testis appears to be more or less broken up and 

 invaded by strands of tissue, which carry the ova, in various 

 stages of maturity, into its interior. A still more complicated 

 condition is shown in fig. 4. Here the most of the gonad is 



* Neidert u. Leiber, " (Jeschl.-oi'r. des A7nphioxus" Zool. Jahrb. 

 (Anat.) xviii. 1903; Zaruik, "Geschl.-oig. von Aviphioaus," Zool. .Iftliib. 

 (Anat.) xxi. 1 90.^5. 



