178 SUMMABY OF CURIIENT RESEARCHES RELATING TO 



in their mode of grouping, their form, and structure with those ob- 

 tained by M. Daubree by fusing peridote with wrought iron [fer doux). 

 (9) Deducting the pulverulent and metallic substances, and the un- 

 crystallized encrusting materials, ordinary meteorites consist only of 

 crystalline elements united to form chondrites ; this is proved by 

 disintegrating them by rubbing or by the use of acids. 



Red Pigment of Invertebrates (Tetronerythrine).* — At the 

 coast it may readily be observed that a red coloration is very 

 common among invertebrate animals, and even fishes. And accord- 

 ing to C. Mereschkowsky, even the animals coloured yellow, brown, 

 green, and black, have always a scarlet red pigment, which in their 

 case is hidden by others. The red pigment, he finds, is always the 

 same substance, viz. that known as tetronerythrine ; he has verified 

 its presence in one hundred and four species (invertebrates and fishes). 

 The question arises, what is the physiological role of this widely 

 expanded substance ? The author finds evidence that it corresponds 

 to haemoglobin in higher animals : serving for cutaneous respiration 

 by virtue of its great afiinity for oxygen. Thus, as regards distribu- 

 tion in organs, wherever oxygen has to be largely consumed by the 

 tissues, there tetronerythrine is abundant. This is illustrated by 

 skin tissues in immediate contact with the oxygen of the water ; by 

 the organs of respii'ation (e. g. in sedentary Annelids the tetronery- 

 thrine is concentrated in the branchiae, the rest of the body having 

 only traces) ; by muscles, and such an organ as the muscular foot of 

 Lamellibranchiates. Nest, as to distribution in the animal kingdom : 

 sedentary animals are often redder, and have more tetronerythrine 

 than errant animals ; the latter which, by constant change of place, 

 are always in water holding plenty of oxygen, not having the same 

 need of a special substance to increase the oxygen absorbed by the 

 tissues. Then the fact that tetronerythrine occurs by preference in 

 invertebrates, where haemoglobin is wanting (and only exceptionally 

 in higher animals), points to similarity of function in these sub- 

 stances. It is further pointed out that animals provided with yellow 

 cells (parasitic algae), which are proved to produce free oxygen in the 

 tissues, are without tetronerythrine, or have very little of it. 



Mollusca. 



Maturation, Fecundation and Segmentation of Limax campestris.f 

 — In this remarkable contribution to embryology, E. L. Mark deals in 

 the first sixty jjages with his own observations ; the rest of the paper 

 falls under the head of bibliography, and we have nearly three hundred 

 pages devoted to a consideration first of the egg-envelopes and yolk 

 of Limax, and secondly of a review of maturation, fecundation, and 

 cell-division ; asters, quiescent nuclei, and nuclei in division are 

 successively taken in review ; and for the last, tissues as well as 

 plants are examined ; the paper concludes with theoretical considera- 

 tions and conclusions, in which attention is drawn to such important 

 points as the promorphology of the ovum, asters, origin of nuclei, and 



* Comptes Eendus, xciii. (1881) pp. 1029-32 ; Nature, xxv. (1882) p. 276. 

 t Bull. Mus. Comp. Zool., vi., No. 12 (1881) pp. 173-625 (5 pis,). 



