980 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Development and Structure of Pedunculated Eyes of Bran- 

 chipus.* — Prof. C. Clans finds the rudiments of the Lateral eyes of 

 Branchipua in meta-nauplius larva?; the pigment and the first crys- 

 talline cones appear in the lateral parts of the eyes, the derivates of 

 the hypodermal cells being divided into a superficial layer for the 

 formation of the cones, and a deeper layer for tlie nervous roils and 

 pigment. '1 he optic ganglion in divisible into a distinct retinal part, 

 and a proximal segment which is united with the cerebrum. 



The eye of Branchipus is simpler than any other pedunculate eye; 

 special pigment-cells being absent in the vicinity of the nerve-rods 

 and of the crystalline cones; the cornea is not facetted, and, as in 

 the eyes of Phronima and of Apus, there is a special layer of hypo- 

 dermal cells above the crystalline bodies; this layer, the absence of 

 facets and of special pigment-cells, together with the presence of 

 interstices for the circulation of the blood in the nerve-bundle layer, 

 and the layer of crystalline cones, are the charaeteristics of the 

 Arthropod compound eye ; the appearance of corneal facets is due to 

 the deficiency of the superficial hypodermal layer, and is a secondary 

 phenomenon. 



Vermes. 



Genital Organs of Hirudo and Aulastoma.f — M. C. Chworo- 

 stanky, in opposition to M. Eemy Saint Loup, asserts that the 

 testicles are generally arranged in nine and not ten pairs ; the inde- 

 pendent glands of the French anatomist are the folds of the wall of 

 the vas deferens ; he also makes some additions and other corrections 

 to what is known with regard to the gonads of these two leeches. 



Reproductive Organs of Earthworm:. } — As the result of his 

 investigation of the reproductive organs of Lumbricus Dr. C. Keuland 

 has established the following conclusions: — 



1. The stroma of the ovary is by no means homogeneous. 



2. Each ovum contains two solid germinal spots. 



3. The receptacula seminis are ontogenetically invaginations of 

 the integument, and with this a multiplication of the unicellular 

 glands is associated. 



4. The seminal vesiele is to be regarded in toto as testis. 



5. There are thus two testes. 



6. Part of the reproductive material is used in the cocoon as 

 nutriment for the more vigorous. 



Endothelium of Lumbricus and Arenicol?.§ — M. H. Viallanes 



finds that the endothelium which invests the muscular bundles of 

 Arenicola are distinguished from those of Lumbricus by the irregular 

 contour of the cells of which it is composed. The endothelial 

 covering of the ganglionic chain of Arenicola is probably incomplete, 

 as the nervous centres remain closely connected with the hypodermis. 



* Anzeig. K. Akad. Wins. Wien, 1886, p. 60. Cf. Ann. and Mag. Nut. 

 Hist., rviii. (1886) pp. 79-80. 



t Zool. Anzeig., ix. (1886) pp. 446-8. 



j Verhandl. Naturh. Ver. Rheinland, xliii. (1S86) pp. 35-54 (1 pi.). 



§ Ann. Sci. Nat., xx. (1886) Art. No. 3, 10 pp., 1 pi. 



