Mr M c Dowall, A Preliminary Note, etc. 309 



A Preliminary Note on the Maiotic Phenomena in the Eggs 

 of the Hermaphrodite " Angiostomum nigrovenosum " (" Ascaris 

 nigrovenosa"). By S. A. M c Dowall, B.A., Trinity College. 



[Received 23 February 1906.] 



It was suggested to me by Mr Purmett, of Caius College, that 

 an investigation of the maturation processes in the sex cells of 

 Angiostomum nigrovenosum, Rud. {Angiostomum, Duj.; Ascaris, 

 Linn.; Rhabdonema, Ktitz.) might lead to interesting results. As 

 is well known this nematode presents the unique phenomenon 

 of a protandrous hermaphrodite generation, alternating with a 

 dioecious*; and it seemed very possible that there might be 

 corresponding peculiarities in the maturing sex cells of the worm. 



The technical difficulties of the examination proved unex- 

 pectedly great, owing to the irnperviousness of the cuticle, and 

 also to the minute size of the dioecious or Rhabditis form. The 

 work was much delayed by illness, and I have only been able to 

 obtain satisfactory results in the hermaphrodite generation. 



As, however, the maioticf phenomena in the oocytes of this 

 generation present features of some interest, it seemed worth while 

 to publish a preliminary account now, in the hope of supplementing 

 the description later with a fuller account of them in both the 

 hermaphrodite form and the Rhabditis. The preservative used 

 was Petrunkewitsch's fluid J, but special methods of application 

 were resorted to in order to ensure satisfactory results. The 

 sections were stained with iron-haematoxylin and orange G. 

 The onset of the maiotic phase is well marked. The nucleoli are 

 large ; they are generally not vacuolated, and only in very rare 

 instances is more than one present. 



The first sign of activity manifests itself in an increase in the 

 linin network, which becomes very dense. " Chromatic clouds " 

 appear in the nodal aggregations of linin, and these gradually 

 become denser, spreading along the linin threads, and forming the 

 distinct chromatin network, with nodal chromatin-masses. 



The reticulum next splits into definite chromosomes, apparently 

 twelve in number. 



* E. Mecznikow, Archiv fiir Aunt. u. Phys. {Mailer's Archiv), 1865. 

 t I.e. Reduction, v. Farmer and Moore, Q.J.M.S., Vol. 48, Part iv. 1905, p. 489. 

 X A. Petrunkewitsch, Zool. Jiilirb., Abtheilung fiir Ariat. u. Ont. der Thiere, 

 Bd. xiv. p. 576. 



