ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 683 



analysis has not been obtained. Forty-two colonies were dealt with, 

 and the results of the investigation are thus summed up. The oral 

 verticil of four capitate tentacles tends to be constant, except in a few 

 cases where all the tentacles were irregularly scattered. The variations 

 in symmetry show how easily H. cooperl could have descended from a 

 Pennarian ancestor, where the capitate tentacles are present in con- 

 siderable number, and are quite irregularly scattered. An important 

 point to consider is whether the distribution of symmetry in a population 

 throws any light on the steps by means of which this symmetry was 

 acquired. It may be assumed that symmetry of this nature could not 

 easily be acquired by imperceptible steps : it would more readily be 

 acquired by larger steps, or in other words by discontinuous variations. 

 The amount of material was not sufficient to indicate whether locaUty 

 or sex has any effect on the arrangement of the tentacles. 



New Hydroid Genus from Natal Coast.* — E. Warren describes 

 ParawrUjldia robust a g. et sp. n., which has been found at several places 

 on the Natal coast. It is not very common ; it occurs attached to sea- 

 weeds and sponges in the rock pools near the low-water line. The 

 general appearance of the colony is like that of Perigonimiis ; the 

 endoderm of the hydranth is red, as in several species of that genus, 

 but the reproductive bodies are fixed gonophores, whereas in Perigoni- 

 mus free medusse are produced. On the whole it appears to come 

 nearer to Wrightia, although distinct also from that genus. The name 

 Parawrightia robasta is proposed to indicate the relationship. An 

 account is added of a supposed Schizophyte occurring in the gouopliores. 



Porifera. 



Factors in Production of Spicules.!— W. Woodland offers some 

 preliminary considerations on this subject. He defines a spicule as a 

 "hard, crystalline or colloidal deposit, of more or less extended and 

 often definite and complex fonu, always possessing curved surfaces and 

 never plane facets, formed initially within a cell or a cell fusion, and 

 whose subsequent growth, which may be intra- or extra-cellular, is due 

 either solely to the activity of the mother-cell or cells and its or their 

 division-products if formed, or also partly to the activity of cells not 

 derived from the original mother-cell or cells." A considerable body 

 of argument is adduced, showing that we are " for the present justified 

 in dechning to enterfeiin the hypothesis of the inheritance of spicule 

 forms." Three factors in their production are conceivable : {a) The 

 gross mechanical factor, or the shaping of a structure due either to 

 actual contact with surrounding objects, or to the configuration of the 

 secreting substance ; {b) the influence at a distance — actio in distans — 

 of different parts of the organism on the scleroplasm ; and (<;) the 

 factor which produces crysttillomorphs. These three are in turn con- 

 sidered. While it is admitted that prolonged investigation is still neces- 

 sary before we can hope to interpret in a satisfactory manner the 



* Anuals Natal Govt. Museum, i. (1907) pt. 2, pp. 187-208 (2 pis.), 

 t Quart. Journ. Micr. Sci., li. (1907) pp. 55-79. 



