RESEARCH SEMINAR OF^THE MARINE BIOLOGI- 

 CAL LABORATORY. 



i. ZOOLOGY, SEASON OF 1904. 



July 5. Work on the Life Histories of some Cestode Para- 

 sites of Fishes. By WINTERTON C. CURTIS. 



July 8. Conditions that Determine the Relative Position of 

 Chromosomes in Mitosis. By RALPH S. LILLIE. 



July 12. The Physiology of the Invertebrate Heart. By A. 



J. CARLSON. 



The following points were demonstrated by drawings and 

 graphic records : 



I. With the exception of Mytilus, in which the results are not 

 conclusive, the auricles and the ventricle of the lamellibranchs 

 (My a, Tapes, Venus, Hennites, Pecten, Cardiuni) are supplied 

 with inhibitory nerves from the visceral ganglion or ganglia. 

 These fibers reach the heart in the renal nerves and enter at the 

 base of the auricles. No nerves enter the heart along the 

 aortae or the rectum. 



The heart of the prosobranchs (Haliotis, Lucapina, Natica, 

 Sycotypus) and the tectibranchs (Aplysia, Bulla, Pleurobranchcza) 

 is supplied with accelerator nerves from the visceral ganglion or 

 ganglia. These nerves enter the ventricle at the aortic end. 

 Some fibres may also reach the ventricle through the auricular 

 walls. The auricular nerves enter the auricle at its base. 



The heart of the nudibranchs is supplied with regulative nerves 

 from the brain or supraoesophageal ganglion. In Montereina 

 these nerves appear to be of the accelerator type only, while in 

 Triopha both inhibitory and accelerator nerves are present. 



The auricle of the slugs (Liuiax, Arioliuia.v) and the snail 

 (Helix) is supplied with both inhibitory and accelerator nerves 

 from the suboesophageal or pleural ganglion. These nerves 

 enter the auricular musculature at the base of the auricle. The 

 innervation of the ventricle of these pulmonates appears to be 

 less uniform. The ventricle of Helix is supplied with both in- 



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