ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 731 



rim must be regarded as the primitive enteric involution, like the inflected 

 arc in Elasmobranchs or Amphibians. The important feature in the 

 teleostean egg is that the germinal matter is so concentrated at one pole 

 as to have little more connection with the yolk than that of juxtaposition ; 

 if this be so,' a less distorted and more primitive condition may have been 

 resumed ; this supposition explains how, with a great bulk of yolk, the 

 blastopore of osseous fishes is symmetrical, and coincides with the entire 

 inflected margin of the germ. 



Development of Ichthyophis glutinosa.* — Herren P. and F. Sarasin 

 found two kinds of dermal sensory organs in the skin of the larvae and the 

 oldest embryo of Ichthyophis glutinosa. The nervous elevations which are 

 found in other Amphibia are very well developed ; beneath each organ the 

 nerve forms a small ganglionic swelling, the elevations are set on a 

 papilla of the cutis which incloses a large blood-sinus, and through the 

 middle of this the nerve passes. The basal processes which the authors first 

 regarded as nervous are now looked upon as being connective-tissue- 

 fibres. 



In addition to these there are organs of another kind in the skin of the 

 head ; these are flask-like structures with a narrow neck open to the exterior ; 

 as a rule, these organs consist merely of two layers of cells, the inner being 

 truly sensory, and the outer supporting ; the sensory cells have long stiff 

 hairs which project into the cavity of the organs, and on them there moves 

 a refractive club-shaped body, which is so held by the hairs that it nowhere 

 touches the wall of the organ ; we seem here to have to do with a true 

 dermal auditory organ, and it is interesting to observe that the sensory colls 

 of this dermal organ are exactly like the auditory cells of the true ear of 

 Ichthyophis. The club-like body is easily dissolved, and appears to be 

 formed by the secretion of the supporting cells of the organ. The re- 

 semblance of the organs of the lateral line to auditory organs has been 

 frequently noted ; here, in Icththyophis, the organ may be justifiably called 

 a subsidiary ear. Later in development it appears to undergo glandular 

 degeneration. 



Why do certain Fish-ova float ?t — After referring to a statement 

 by Prince as to the buoyancy of certain fish-ova, Mr. J. A. Ryder gives 

 some notes on the subject. 



There are three chief types of buoyant ova : (1) Those in which the 

 specific gravity of the yolk is diminished, as in the cod ; (2) those in which 

 large oil-drops in an excentric position aid in causing the eggs to float ; and 

 (3) those in which a single large oil-drop causes the ovum to float even in 

 fresh water. These types are connected by intermediate forms. As a rule 

 the buoyant ovum has a single large oil-drop imbedded in the vitellus at 

 the opposite pole to the germinal disc ; buoyant ova float singly ; are 

 transparent ; have thin membranes which do not adhere. Macropodus 

 venustus, a fresh-water form, has buoyant ova, in which the relative 

 volume of the oil-droj} is greater than in any other form ; and in this form 

 the oil is the solo cause of the buoyancy, since the plasma, when freed, 

 sinks. With the exception of this ovum, buoyant ova require water of a 

 greater density than 1 • 014. 



Fermentations by Protoplasm of a recently-killed animal. | — M. 

 Fokker states that he has been able to demonstrate that the fermentations 

 which, since the experiments of Pasteur, it has been usual to regard as due 

 to microbes, are produced also by the protoplasm of a normal tissue. If a 



* Zool. Anzeig., x. (1887) pp. 194-7. t Amer. Natural., xx. (1886) pp. 986-7. 

 J Comptes Kendus, civ. (1887) pp. 1730-2. 



