MUSEUM OF COMPARATIVE ZOOLOGY. 145 



Cyclogaster lineatus (Liparis lineatus Auct.). 



The ovaries of this species contain ripe eggs in May, the time at 

 which I examined them. The largest eggs were about 0.63 mm. in 

 diameter, the membrane averaged about 0.043 mm. in thickness. The 

 zona radiata seems to be filled with small spaces connected by the much 

 finer radial canals (Fig. 40, Plate III.), the spaces causing the latter to 

 appear moniliform. Near the inner and outer margins of the zona the 

 canals are simple tubes, as in most other fishes. 



The eggs next in size are 0.25 to 0.30 mm. in diameter; their zona is 

 always only half as thick on one side as it is on the opposite, the change 

 in thickness being nowhere abrupt. In eggs of this stage the zona is 

 traversed hy simple pore-canals, which are indistinct near its outer sur- 

 face. In some cases (Fig. 41, Plate III.) the transition from the inner 

 to the outer portion is so abrupt that the zona appears to be composed 

 of two layers of unequal thickness, — an outer, thinner, more nearly 

 homogeneous and unstained, and an inner which is thicker, more dis- 

 tinctly striate, and usually faintly stained. 



The micropyle (Figs. 42-44, Plate III.) was observed only in eggs 

 about 0.16 mm. in diameter. As in the case of Pygosteus it seems to"lie 

 in a plane perpendicular to the long axis of the ovary. The micropyle is 

 a long narrow tube, with parallel sides, in a local thickening of the zona. 

 This increase in the thickness of the zona affects the outline of the inner 

 surface more than that of the outer, and is entirely independent of the 

 above mentioned gradual change in thickness between opposite poles of 

 the egg. It is produced principally by additions to the inner surface of 

 the zona. The outer surface is slightly elevated at a little distance from 

 the micropyle, but is abruptly depressed immediately over it. The reg- 

 ularity in the arrangement of the nuclei of the granulosa cells is dis- 

 turbed in the immediate vicinity of the micropyle, where the whole layer 

 is slightly thickened. Usually an enlarged single nucleus lies immedi- 

 ately above the micropylar canal (Fig. 44). 



On the Number of Egg Membranes. 



The views held concerning the number of egg membranes in teleosts 

 have been many and various. Authors have generally been agreed about 

 the presence of a membrane perforate with radial canals, the zona ra- 

 diata ; but doubts have been raised by Ryder whether this membrane 

 is always present. He ('82 c ) found no striations in the egg membrane of 



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