i 74 SCIENCE PROGRESS 



in the Actinia and Metridium,'m which, for the first time, there appears the dawn of a 

 reflex act. The species Cordylophora are studied in detail and are fully recorded, 

 the twelve or more sets of muscles (contracting protoplasm) constituting the only 

 effector by means of which, through the stimulation of touch orheat,the nervous sys- 

 tem in the Actinice is capable of reacting — the cilia, mucous glands, and the nettle 

 cells being apparently uncontrolled by any nervous mechanism whatsoever. 



The study of the sensitivity of the marginal bodies in the Medusa shows a 

 gradual development of the receptor element, as isolated sections of this may be 

 associated with the whole — thus anticipating the co-ordinated and unified action 

 of the vertebrate response. The "nerve net," which confers autonomy upon the 

 part supplied, is an illustration of the diffused non-centralised nature of action and 

 response to stimuli, as contrasted with action where there is a central controlling 

 nervous system giving rise to unified movement. 



In regard to the origin of Mind, the author points out that in the Actinia 

 behaviour is conditioned by the immediate environment, and the organism is 

 merely a reactive mechanism, or, in other words, a bundle of reflexes ; reaction 

 being caused by present stimuli rather than being a response due to internal states 

 brought about by past activities. The last chapter is a continuation of analogous 

 research upon the Hydroidae with Corymorpha ftahfia as type, and in which, 

 although there is no organised nervous centre, there is a reflex control of the 

 elementary muscular substance. 



The conclusion summarises the results of investigations by the author and 

 others in regard to the earliest dawn of a nervous system, which, in the most 

 elementary kind, exists in multicellular animals as smooth muscular fibre. This 

 acts as an independent effector without any trace of a nervous system. The next 

 step in the higher Coelenterata is the development from epithelial cells of a receptor 

 area, which shows the intimate relation between the epiblastic elements of the 

 nervous and epithelial cells, these becoming responsive to chemical pressure 

 (touch), heat and light stimuli, and in the sea anemones existing as the proto- 

 neurone intermediately placed between the sensory area and the muscle effector, 

 the final neurone being due to the extension of processes of the cell, the union of 

 cells being further effected by intercalary or inter-nuncial neurones, which, in the 

 fully-developed brain, account for its extreme complexity. There are several pages 

 of bibliography which cannot but add to the usefulness of a volume devoted to so 

 specific a study. Robert Armstrong-Jones, M.D. 



What is Psycho-analysis ? By Isador H. Coriat, M.D. [Pp.124.] Kegan 

 Paul, Triibner & Co. (London : 1919. Price y. 6d. net.) 



It is two-thirds of a century since Sir William Hamilton arranged the phenomena 

 of Mind under the three categories of cognition, feeling and conation. He 

 maintained that these were discovered by an analysis of consciousness, or by 

 introspection, and he instanced the three phenomena firstly of Knowledge, then of 

 Feeling, i.e. of Pleasure and Pain, and lastly of the Will and Conation, by the 

 illustration of a person approaching a picture and becoming conscious, in the first 

 instance, of perceiving a certain complement of colour and form which was cognition ; 

 secondly, of experiencing certain feelings, either of gratification if the picture be a 

 masterpiece, or of a more mingled character if the picture be of indifferent merit ; 

 and, thirdly, that these experiences would be succeeded by a growing desire to 

 become the possessor of the picture, and, as a consummation of the desire, the will 

 would tend towards its possession. 



These three groups of elementary mental units were compared to the red, 

 yellow and blue rays of the solar spectrum, with their three separate qualities, 



