SCIENCE. 



[N. S. Vol. III. No. 54. 



ment, varied by physiological contributions 

 from Dr. Parker. 



Dr. Dean (Columbia) discussed the gas- 

 trulation of teleosts from a comparative 

 point of view, urging that a key to its in- 

 terpretation must be sought in the develop- 

 ment of ganoids. Lepidosteus, Acipenser 

 and Amia form a progressive series culmi- 

 nating in the teleost, the length of the 

 neural plate gradually increasing from 90° 

 to more than 200°, the ventral lip of the 

 blastopore becoming less clearly marked, 

 and the neural plate becoming more and 

 more concentrated towards the median 

 plane. The following interpretation of the 

 of the parts of the teleostean gastrula was 

 adopted : dorsal and ventral lip of the 

 blastopore as identified by Haeckel, Kyder, 

 H. V. Wilson and others ; ' ventral meso- 

 blast ' of H. V. Wilson as entoblast; 

 KupfiFer's vesicle as the notch under the 

 dorsal lip of the blastopore, caused mechan- 

 ically in the growth of the Eandwulst ; 

 periblast as the highly differentiated outer 

 layer of the yolk mass, which enables the 

 enclosing growth of the blastoderm, yet 

 preserves in a most perfect way its incre- 

 mental relations with the adjacent tissues 

 of the embryo. In view of the presence of 

 medullary folds in Lepidosteus and Acipen- 

 ser, rudimentary in the former, perfect in 

 the latter, the solid neural plate of the em- 

 bryonic Teleost must be regarded as a 

 secondary condition, due to the mechanical 

 needs of the embryo in its precocious 

 growth. 



Dr. Parker's (Harvard) first paper con- 

 sidered the pigment changes in the eye of 

 the shrimp Pakemonetes with especial refer- 

 ence to the nature of the reflex-action in- 

 volved.* The pigment-changes called forth 

 by the action of liglit take place in the 

 typical manner in animals after section of 

 the optic nerve, showing that they are not 



* Unfortunately an adequate review of this paper 

 eannot be given. 



determined by a reflex center in the cerebral 

 ganglia, but by a local action which may be 

 due to the direct action of light on the pig- 

 ment cells. 



In his second paper Dr. Parker gave an 

 account of experiments on sea anemones 

 which led to interesting results. Tliese 

 animals respond in a definite manner either 

 to solid or dissolved food matters, and the 

 sense by which they are perceived resides 

 in the tentacles, the oral disc and the lips 

 of the mouth. Food is taken in thi-ough 

 the action of cilia covering the tentacles 

 and the entire oral region. Those of the 

 lips and oesophagus work inwards ; those of 

 the tentacles work outwards towards the 

 lips. If nutritious substances are placed on 

 the tentacles the latter bend inwards to- 

 wards the mouth, into which the food is 

 therefore swept bj^ the cilia; innutritious 

 bodies, on the other hand, cause the tenta- 

 cles to be extended so that such bodies are 

 carried out to the tips and thrown ofi". 

 The most interesting results relate to the 

 reversal of the ciliary action that occurs un- 

 der certain conditions. Inert substances, 

 such as carmine, may be at first swept into 

 the moutli, but are afterwards thrown out 

 by a reversed action of the oesophageal cilia. 

 The action of the cilia is therefore under the 

 control of the animal, which is moreover 

 capable of certain" degree of education. If 

 animals be fed with fragments of meat 

 and pieces of paper soaked in meat juice, 

 both are at first taken into the stomach, 

 but the paper fragments are afterwards 

 thrown out. After a number of trials 

 (seventeen or more) the animal learns to 

 discriminate, the paper being rejected and 

 the meat swallowed. Their memory is 

 however short lived, for on the following 

 day the lesson must be learned anew. 



Dr. Stiles, of Washington, discussed a 

 number of new points in the anatomy of 

 tape worms, and exhibited a large number of 

 plates of new and little-known species. He 



