ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 879 



Innervation of the Heart, and Influence of Poisons on Lamelli- 

 branchiata. * — E. Yung commences by pointing out that the soft- 

 ness of their tissues, the delicacy of the walls of their vessels, and 

 the extreme reduction of their nervous system, are considerable ob- 

 stacles to the study of the physiological processes of Lamellibranchs. 

 He describes the heart as being provided with fibres from the posterior 

 or branchial ganglia, which accelerate the cardiac movements by in- 

 creasing the number of the pulsations. Electricity, applied directly to 

 the heart, only produces a local effect ; the portion of muscle between 

 the poles is arrested in its contractions, but the remaining mass of the 

 heart continues to beat. No real change appears to be effected by 

 removing the heart from the influence of the oesophageal or the pedal 

 ganglia ; elevation of temperature quickens its movements, up to 

 40° C. ; fresh water somewhat rapidly kills them. Curare, when in a 

 weak solution, appears to have no effect ; but when very strong, it slows, 

 though without absolutely stopping, the movements of the animal ; 

 it would seem to have no direct action on the heart. Strychnine has 

 but a temporary effect ; whatever be the dose, it only provokes some 

 convulsive movements in the muscles of the siphon and edge of the 

 mantle, and never gives rise to any true tetanus. A feeble dose of 

 nicotine acts as an irritant, a strong one kills ; under its influence the 

 heart increases considerably in volume. Digitalin only acts on the 

 heart when it is brought into direct contact with it, and it then 

 diminishes the number of pulsations. Upas antiar has, similarly, no 

 action on the heart unless brought into direct contact with it, when it 

 produces a paralysis. Sulphocyanide of potassium in a strong dose 

 stops the heart in diastole, and completely kills it. Anodonta anatina, 

 Solen ensis, and Mya arenaria, were the chief subjects of experiment. 



MoUuscoida. 



Development of Doliolum.t — B. Ulianin, after describing the 

 formation of the ovum of this little-known form of Tunicates, states 

 that a delicate cuticular membrane is formed by the cells of the 

 egg-follicle, which persist until the appearance of the fully formed 

 Doliolum. Cleavage is at first regular and complete ; after a time it 

 becomes irregular, and goes on much more rapidly on one than on 

 the other side of the egg. Invagination was occasionally observed, 

 but the author does not wish to speak definitely as to the mode of 

 gastrulation. 



In the next observed stage the larva had become provided with 

 a tail ; the extended envelope was seen to contain a sausage- 

 shaped body, the greater part of which consists of a uniform cellular 

 mass, the rudiment of the future nervous system. On either side 

 of this mass there is a mesodermal plate which passes into the 

 tail ; the axis of the latter is already occupied by the characteristic 

 chorda-cells. At the anterior end of the body there is a small vesi- 

 cular enlargement of the ectoderm, which is about to be converted 

 into the provisional anterior ectodermal vesicle. As the tail in- 



* Comptes Kendus, xciii. (1881) pp. 562-4. 

 t Zool. Anzeig., iv. (1881) pp. 473-6. 



