224 SUMMARY OF CUEllENT ilESEAROHES RELATING TO 



the larval stage, when the organism needs more food, it is larger than 

 it is later on. Differences are to be seen in the disposition of the 

 appended ganglia, but the great ganglion frontale is perhaps a 

 separated portion of the cerebrum, which owes its special position to 

 the development of the anterior portion of the digestive tract. 



Pulsating Organs in the Legs of Hemiptera.* — Conflicting 

 opinions have been held regarding the pulsating organs that have 

 from time to time been observed in the legs of certain Hemiptera. 

 W. A. Locy records some observations which enable him to say that 

 these organs are distinct from the muscular system of the legs, and 

 that they influence circulation. Their automaticity was also observed. 

 Specimens for examination were chosen with reference to the trans- 

 parency of their legs, as it is upon this point the success of observation 

 depends. Both larval and adult forms of the genera studied were 

 used, but the best results were uniformly obtained with the larval 

 forms, for the above reason. In some cases special methods were 

 necessary to render the legs transparent enough for observation. 

 For this purpose the integument of the legs was scraped very thin. 

 The organs can be demonstrated in this manner, even in the thick 

 legs of the adult Belostomas. They are most easily seen in the 

 legs of Notonecta and Corixa, but are not so large and pronounced 

 as in the legs of the Nepidse. In the more transparent individuals 

 not only are the organs readily seen, but the circulation of the 

 blood can be watched with a power high enough to bring out the 

 corpuscles. 



7- Arachnida. 



Vitelline Nucleus of Araneina.t— A. Sabatier adopted the follow- 

 ing method in his investigation into the structure of the ova of spiders. 

 The animals were opened while alive in a few drops of alcohol, so as 

 to harden and fix the eggs at once ; sometimes, though rarely, osmic, 

 picric, or acetic acid was used. The eggs were stained with Beale's 

 carmine or picrocarminate of ammonia ; after washing, they were 

 placed in phenicated glycerine. 



The vitelline nucleus was observed in all the Araneids examined ; 

 its presence is ordinarily marked by its affinity for the colouring matters 

 which are taken up by the yolk. Sometimes, indeed, its presence is 

 only revealed by the existence on its surface of refractive granules 

 which mark out its spherical form. In Tegenaria agrestis it is often 

 very distinct. 



This nucleus arises in the neighbourhood of, or even in contact 

 with the germinal vesicle under the form of a mass, which, speaking 

 generally, differs from the yolk by being more finely and evenly 

 granular, by a greater affinity for colouring matters, and sometimes 

 by higher refractive power. It has a massive and not vesicular 

 structure; when it does not undergo stratification it consists of a 

 spherical mass of protoplasm, without membrane or nucleolus, and 

 with no chromatin-plexus, though it probably has some chromatin 



* Amer. Natural., xviii. (1884) pp. 13-9 (1 pi.), 

 t Comptes Eendus, xcvii. (1883) pp. 1570-2. 



