518 JOSEPH STAFFORD, 



of the incorrectness of this. On the outside is a mantle (Fig. 27 M) 

 of closely aggregated small cells with nuclei resembling the young 

 parenchyma cells. It may be two or three cells thick and underneath 

 it is a membrane in which are muscular fibres running in different 

 directions. Some places I have seen inner circular and outer longi- 

 tudinal fibres but at other places the reverse appeared true. Also 

 parenchyma fibres seem to run through the outer mantel and knit 

 into this membrane. The contents appear at first sight as numerous 

 nuclei lying in heaps or in some places scattered with sometimes a 

 more homogeneous fluid mass occupying a portion and all loosely dis- 

 posed in the inner space. Upon close observation the nuclei are found 

 to lie in cells of spherical or polygonal form whose boundaries are 

 recognized only as delicate lines. The fluid part is a mass of fully 

 formed spermatozoa lying in a body of liquid or, as I have seen very 

 distinctly in living animals, as winding streets among the groups of 

 sperm-mother cells. In young animals where the yolk glands are not 

 complete the testis already contains perfectly formed sperm and in 

 fact this seems to be the time of greatest production of them when 

 they are conducted through the oviduct before it is blocked up 

 with eggs. 



No clearly traceable centripetal order of development comparable 

 with that in the ovary is perceptible here although very small cells 

 may be discovered towards the surface lying among the larger ones. 

 The nuclei are of difi"erent sizes and their chromatin shows evidences 

 of karyokinetic division (Fig. 29) but the order of the nuclear figures 

 I have not been able to follow. I have seen a few of the large solitary 

 cells (Fig. 29) mentioned by Voeltzkow. They correspond very 

 closely in size and structure with primitive ova. Large cells 

 measure 13 to 18 //, nucleus 9 /ii, nucleolus 4 /.i. Other cells 9 /<, 

 nucleus 5 to 7 fi, generally without nucleolus. 



The vas deferens (Fig. 27 VD) springs from the anterior 

 dorsal part of the testis , its wall being continuous with the mem- 

 branous boundary of that organ. There is no funnel-formed inner ex- 

 tension as figured and described by Voeltzkow. It passes forwards 

 and upwards, then Ijends backwards and ui)wards through the septum 

 and again forwards suddenly swelling into the vesicula seminalis, 

 a tube of very diff'erent calibre depending on its contents. Distended 

 with spermatozoa (Fig. 9 VS) it measureSj,0,07 mm in diameter while 

 the vas deferens measures only 0,014 mm. On the walls of the vas 

 deferens, bulging into the lumen, are numerous nuclei while in the 



