OF BDELLOSTOMA AND A TELEOSTEAN OVUM. 249 



of the two opposite poles of the ovum is not peculiar to the Myxinoicls. It is 

 as certain as an inference from the unfertilised ovum can be, that the 

 segmentation of the egg of the Myxinoids is meroblastic, as in Teleosteans, and 

 thus in two points the Myxinoid ovum agrees with the Teleostean, and differs 

 from that of Petromyzon, while in respect of the mass of the yolk the 

 Myxinoids agree more with Elasmobranchs. 



I have not succeeded in identifying the species of fish to which belong the 

 eggs above described. The eggs of several species are known to be provided 

 with filamentous processes. In the Scombresociclae the filaments are equal in 

 length to the diameter of the ovum, and are uniformly distributed over the 

 surface of the membrane. The filaments in this family were first described by 

 Professor Haeckel.* John A. Eyder gives a very clear and complete account 

 of them in the Bulletin of the U. S. Fish Commission, 1881, vol. L, as studied in 

 Belone longirostris. In Chirostoma, one of the Atheriniclae, Ryder found 

 there were only four filaments attached at one pole of the egg close together. 

 In this latter case the filaments were during development closely wound 

 round the vitelline membrane in one equator of the sphere, so that the 

 method of their formation differs from that of the Myxinoid filaments, which 

 are perpendicular to the surface of the membrane throughout their growth in 

 the follicle. 



Filamentous processes of the vitelline membrane occur also in the family 

 Pomacentridae ; they have been described by Hoffmann in Heliastes chromis 

 of the Mediterranean (see Konink. Akad. d. Vetensk. Amst., vol. xxi.). Here 

 they occur at one end only of the ellipsoidal ovum. They occur also in 

 Gobius and Blennius, but in neither of these cases are two sets of processes 

 present, situated at opposite poles of the ovum. It is thus impossible to say 

 whether the ova described in this paper belong to a fish of the family 

 Scombresocidae among the Physostomi, of the family Pomacentridae, or coral- 

 fishes among the Pharyngognathi, of the family Gobiidae, Blennidae or 

 Atherinidae, or to a species of some other family whose eggs are alto- 

 gether unknown. The ova were obtained on two occasions, each time a 

 single cylindrical "rope," by Mr John Rattray, F.R.S.E., in the Gulf of 

 Guinea. Mr Rattray was on board a steamer called the "Buccaneer" last 

 winter, in the capacity of naturalist, having been invited to accompany Mr J. 

 Y. Buchanan, who was carrying out some hydrographical investigations off the 

 coast of Africa. The eggs were obtained in the following manner : — A small 

 conical buoy was attached at the end of a rope, and along the rope were 

 fastened two or three muslin tow-nets. The whole was then thrown overboard 

 in such a way that the mouth of the tow-net faced whatever current was flow- 

 ing. The eggs were found entangled on the line when the apparatus was 



* Muller's Archiv, 1855. 



