ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 933 



spermato- and karyo-merites into a homogeneous mass. The included 

 microsomata are no longer distinguishable as regards their origin. 



(9) From these microsomata the chromatic portion of the karyokinetic 

 figure is formed. 



Intra-Ovarian Egg of some Osseous Fishes.* — Dr. E. Scharff has ex- 

 amined the ova or ovaries of several osseous fishes, among which the 

 gurnard was a very suitable object of investigation. In speaking of the 

 nucleus and its changes in the smaller ova, the author announces his 

 agreement with the opinion of Dr. Will, that no morphological significance 

 is to be attached to the nucleoli ; they must be regarded as large masses of 

 chromatic substance. With regard to the dark and light-coloured proto- 

 plasm, it is suggested that the dark central protoplasm owes its origin to the 

 nucleus. The egg-membrane, or more or less thick layer which surrounds 

 the egg, and which has been called by seven difierent names, of which 

 " zona radiata" is here preferred, is, in the gurnard, often granular ; within 

 is a much broader layer, which, by its semifluid condition, may be dis- 

 tinguished from the much firmer or elastic zona radiata. In the ripe ova 

 the zonoid layer entirely disappears. 



The follicular layer of the ripe gurnard's egg consists of a layer of 

 closely set cells. With regard to its development, the author's observations 

 are incomplete, but he is inclined to think that it owes its origin to the 

 connective tissue ; at any rate it is formed before an egg-membrane can 

 be seen. 



Development of Osseous Fishes.j — In his first chapter Dr. J. H. 

 List deals with the morphological results which he has obtained by the 

 study .of the Labridte, a family which is well represented in the Adriatic. 



The ripe ovum of Crenilabrus tinea, before fertilization, has a diameter 

 of about 0-9 mm. ; the zona pellucida has an interesting structure, for it 

 consists of two layers. Of these, the outer is formed of regular six-sided 

 prisms, and the inner, which is more homogeneous, exhibits merely a feeble 

 parallel striation. The germinal substance is only incompletely differen- 

 tiated from the yolk in C. tinea, but in C. jpavo it forms a clearer layer 

 round the yolk. On the whole, the arrangement of the germinal substance 

 in the ovum of Crenilabrus exhibits a close resemblance to that of the 

 herring, as described by Prof. Kuppfer ; there are no signs of any germinal 

 processes extending into the yolk. 



The spermatozoa of C. pavo are 18 /a long, of which the tail is 14 /x; at 

 the moment when the sj)ermatozoon is swallowed by the micropylar canal 

 the inner part of the latter is blocked by a feebly refractive mass, and by this 

 means the entrance of other spermatozoa is prevented. Seven minutes after 

 the entrance of the spermatozoa into the egg the directive corpuscle was seen 

 projecting from the funnel-shaped entrance of the micropyle, and within 

 half an hour was extruded. The ovarian contents next underwent con- 

 traction, and within three-quarters of an hour after impregnation a clear 

 space could be noticed between the zona pellucida and the contents ; this 

 space was filled by a colourless fluid, which was probably partly squeezed 

 out from the yolk. The contraction of the germinal substance ceases after 

 about an hour and a half ; and the first segmentation groove appears. This 

 is somewhat excentric. Almost simultaneously an equatorial groove appears 

 at right angles to the first. From the next series of changes it became 

 clear that the form of the nutrient yolk is dependent on the direction of the 



" Quart. Journ. Micr. Sci., xxviii. (1887) pp. 53-74 (1 pi.). 

 t Zeitschr. f. Wiss. Zool., xlv. (1887) pp. 595-615 (3 pis.). 



