36 Mr. E. W. L. Holt on the Ova o/Gobius. 



tnres one can frequently make out a division into two strands, 

 which do not as a rule cross each other, but seem to be merely 

 apposed. 



Filaments or processes are known to occur on the eggs of 

 many Teleosteans, They were found by Hoffmann* in Gohius 

 mtnufus, niger, and other species, IleUasis chromis, Belone, 

 and Blennius. Eigenniann, in his recent excellent memoir 

 " On the Egg-membranes and Micropyle of some Osseous 

 Fishes " t, very clearly describes the development of the fila- 

 ments in Fundulus. In this form they are developed all over 

 the surface of the Q^g^ whereas in our ova the process of 

 attachment is confined to what is presumably the micropylar 

 region. In Fundulus the filaments, originally arising internal 

 to the granulosa, are shown to pass through and, in further 

 development^ to lie external to it, being " bent in a more or 

 less regular manner first to one side and then to another," and 

 " usually follow the margins of the granulosa cells," to which 

 they are '* correspondingly curved." 



Eigenmann also notices rivet-shaped processes on the Qgg^ 

 of FrjgostiiiSj and from certain phenomena noticed in his 

 preparations suggests that " they are from the beginning 

 adhesive." He describes a layer external to the zona in all 

 eggs on which processes are found. Whether such a layer 

 exists here 1 cannot say, nor can I speak with accuracy as to 

 the relation of the attachment process to the zona. 



But it seen)s possible that filaments may be developed in 

 this form as in Fundulus and Pygosteus (though confined to a 

 restricted area), and penetrating the granulosa in due course, 

 so as to lie along the margins of the granulosa-cells, and 

 " being from the beginning adhesive," may have set up with 

 each other intimate relationships, resulting in the formation, 

 by the adhesion and ultimate fusion of their proximal elements, 

 of such a structure as is actually found in the extruded ova 

 before us. The distal parts of the filaments, not coming into 

 contact with each other, and thus remaining independent, may 

 perhaps have extended over a considerable part of the granu- 

 losa, and the whole pedicle of attachment is probably everted 

 on extrusion of tiie <i^g in the same manner as the outer mem- 

 brane of the zona in Osjnerus, described by Buchholz and 

 Cunningham. 



Eigenmann speaks of his " rivet-shaped processes " in 

 Pygosteus as taking a much deeper stain than the membrane 

 (external to the zona) in which they are set. Treated with 



♦ Hoffmnnn, *' Zur Ontogenie der Knockenfiscbe," Verliandel. d. Kon. 

 Ak. T. AVetenschappen, Anist. Deel xxi. 1881, p. 19. 

 t Bull. Milt. Comp. Zool. vol. xix. uo. 2. 



