951 SUMMARY OP CURRENT RESEARCHES RELATING TO 



and other organs is then sketched in a series of very lucid diagrams 

 which make this origin of asymmetry readily intelligible. The theory 

 is compared with the author's investigation of the development of 

 Paludina, and the changes in the lio of the organs are shown in different 

 colours on a diagram composed from three superposed stages. Lastly, 

 the independent torsion of the visceral sac is discussed. 



Innervation of Heart in Helix.*— Signor A. Trambusti has 

 studied the innervation of the heart in Helix pomatia. In his technique 

 he made use of gold chloride and arsenic acid (Golgi's method). The 

 nerves of the cardiac muscles are formed of fibres without medulla, 

 and invested in a nucleated sheath. They form two trunks, the larger 

 of which gives off several filaments, which after forming an auricular 

 plexus, unite in large bundles and pass into the ventricle, while tho 

 smaller branch which traverses the auricle, gives off two or threo 

 branches, forms a small ganglion of seven or eight cells, and then 

 ramifies in the ventricle. The author did not observe any motor 

 plate ; " the nerve-fibres become associated with the muscle-fibres 

 without undergoing modifications of form, and accompany the former 

 along their whole length." 



Nuclear Fusion in Cleavage Spheres.! — Dr. O. Zacharias re- 

 ports that in the ova of Limneeus auricularis he has been able to 

 observe, as a pathological phenomena, the fusion of the first two 

 segments of a dividing egg ; it was most marked when the egg was 

 only surrounded with a little water, and may be due therefore to a 

 want of oxygen. In the cases first observed, the nucleus remained 

 passive, but in a later specimen Dr. Zacharias saw the nuclei approach 

 one another. 



Nervous System and Sensory Epithelium of Cardium.J — Herr 

 K. Drosthas investigated the nervous system and sensory epithelium 

 of Cardium edule, and communicates further some notes on the 

 histology of mantle and siphon. 



I. Tlie nervous system has been carefully described by Duvernoy, 

 whose results Herr Drost has confirmed and amplified. The details 

 are of no special interest. 



II. The sensory epithelium. — Cardium edule exhibits four different 

 kinds of sensory epithelium. Two of these are localized, and two are 

 expanded on the surface of the body. In the first place there is a 

 pigmented epithelium, sensitive to light, occurring on the convexity 

 below the cirrus points. A second kind is exhibited in the combina- 

 tion of supporting, and extremely long-haired sensory cells, which 

 forms the organ imbedded in a depression of the cirrus point. 

 Thirdly, normal penicillate cells occur with very short hairs, and 

 finally broad brush-cells with longer hairs, projecting through the 

 cuticular warts. The associated innervation is very complex. 



III. Histology of mantle and siphons. — After noting the character 



* Rev. Internat. Med. e Chir., ii„ No. 12 (1 pi.). Cf. Rev. Ital. Sci. Nat., 

 ii. (1886) pp. 54-5. 



t Zool. Anzeig., ix. (1886) pp. 400-3. 



X Morphol. Jahrb., xii. (1886) pp. 163-201 (1 pi.). 



