INTEA-OVAEIAN EGG OF SOME OSSEOUS EISHES. 67 



the punctures on the surface of the zona radiata with pores 

 piercing it. Since then, although we occasionally find state- 

 ments to the contrary, the great bulk of zoologists maintain 

 that pores exist in all cases. May not the fact that some of 

 the recent observers have not noticed them be due to the 

 peculiar physiological condition of the egg which Lindgren 

 referred to? Careful investigation of a large number of both 

 intra- and extra-ovarian ova of marine fishes would no doubt 

 help to clear up the matter. 



In the zona radiata of the ripe egg of Gadus morrhua 

 (spirit preparations) no trace of a striation could be made out 

 with a magnifying power of about 800 diam. Cunningham, 1 

 however, has seen the stripes in ova of the same species which 

 were prepared with Perenyi's fluid, and I firmly believe they 

 exist in all cases. As the same observer has recently pointed 

 out, the pores may occasionally (Myxine glutinosa) be 

 branched. 



To return to His' zonoid layer, I stated my reasons for con- 

 sidering it as one of the egg-membranes, although all previous 

 observers looked upon it merely as the modified external part 

 of the yolk. 



The ova of Blennius pholis have one layer only. The 

 zonoid layer is always absent. 



In speaking of the zonoid layer, His 2 says " It is probable 

 that it belongs to the zona radiata, but the detailed history of 

 both formations has still to be done." 



A question which has occupied the attention of many modern 

 observers on this subject is whether the pores of the zona 

 radiata receive processes from the surrounding follicular cells. 

 It seems to have first been suggested by Waldeyer 3 that the 

 egg-membranes are secretions from the follicular epithelium, 

 and that the latter sends prolongations through the pores into 



1 Cunningham, " On the Structure and Development of the Reproduct. 

 Elements in Myxine glutinosa," 'Quart. Journ. Micr. Sci.,' 1886. 



2 His, W., 'Untersuchungen liber d. Ei und d. Eientwickl. bei Knochen- 

 fischen,' Leipzig, 1873. 



3 Waldeyer, ' Eierstock und Ei,' Leipzig, 1870. 



(i 



