Anatomical structure of Aspidogaster conchicola. 525 



outer margin of the first turn, and 0,12 X 0)2 mm in cross section 

 at the broadest part, with the larger diameter approximately dorsi- 

 ventral. It is bounded by a thin fibrous membrane with here and 

 there a nucleus resembling those of the parenchyma cells. This outer 

 coating is not at all to be compared with that of the testis as 

 VoELTZKOw has done. The bladder-like, vacuolated parenchyma cells 

 become simply more and more compressed and smaller as they near 

 the outer limits of the ovary. The contents of this organ consists of 

 closely packed cells having very different sizes and differences in the 

 minutiae of their cell structure. But there is a distinctly marked 

 order of growth from the youngest cells to the perfectly formed pri- 

 mitive ova. At the anterior, broad, blind end of the organ the young 

 cells are engaged in growth and fission. Here the small nuclei of 

 4 II diameter are deeply stainable, with chromatin dots, and are packed 

 so closely together that cell protoplasm is unrecognizable. A little 

 farther inwards each nucleus has acquired a rim of protoplasm, retained 

 its chromatin dots, possesses a small nucleolus, and has itself in- 

 creased in diameter to 6 or 7 ^i. Cells in the centre of the ovary 

 have their considerable quantity of protoplasm compressed into long 

 angular shapes. Their chromatin forms a pale reticulum in the 

 vacuolated, slightly elliptical nuclei of 14 /n in length, with nucleolus 

 4 iLi. From this on the ova increase in size, some of their nuclei 

 possessing a large and a small nucleolus, others two equal sized 

 nucleoli. They assume a curved arrangement in rows with the con- 

 cave surface towards the oviduct. In the smaller anteriorly curved 

 portion of the ovary they reach their maximum size and pass into 

 the first segment of the oviduct, called by Voeltzkow Tuba Fallopii. 

 This begins about the middle of the first arm and continues round 

 the second bend and backwards to the entrance of the Laurer's canal. 

 VoELTZKOw's description of this is quite correct as I have proved 

 both in living animals and from sections that fall along the tuba. 

 The rings, dividing the tuba into successive chambers and forming so 

 important a landmark in determining the situation of the organs in 

 the living animal, begin in the developing oviduct as thickenings on 

 the inside in each of which is a nucleus. Fertilization may take 

 place here, for I have seen spermatozoa in lively activity as far in- 

 wards as the third chamber from the ovary. All along from 

 the narrowed end of the ovary are exhibited nuclei on the inside 

 of the walls and in some places definite cell boundaries. But 

 the portion between Laurer's canal and the vitelline duct shows 



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