28 Anatomy of Sagartia Schilleriana [No. 1, 



On the anatomy of Sagartia Schilleriana and Membranipora 

 Bengalensis, a new Coral and a Pryozoon living in brackish water 

 at Port Canning ; — by Ferd. Stoliczka, Esq. Ph. D. } F. G. S. 

 Palaeontologist of the Qeol. Survey of India. 



[Received 3rd June, 1868.] 



Special interest is always attached to the study of any organic forms, 

 found living under unusual and sometimes anomalous conditions, 

 inasmuch as these forms very often represent peculiar types of organi- 

 sation, adapted to the peculiar circumstances under which they live. 



In a theoretical point of view, there exist, we may say, in each speci- 

 fic organism a number of forces which, by their harmonious action, 

 produce a certain stable equilibrium between the organisation of the 

 animal, and the influences of the medium in which it lives. Should it 

 now happen that the animal is, either voluntarily or accidentally, 

 placed, under conditions different from those under which it formerly 

 existed, and further, should the influence of these external agencies be 

 so great as to overthrow, or be not sufficient to maintain this equili- 

 brium, it devolves upon the organism to restore this balance, or to be 

 dissolved into various other forces. The latter case need not occupy 

 here our attention any further ; but as to the formei', we may observe 

 in general that the amount of the changes in the organism, necessita- 

 ted for the purpose of restoring the disturbed or unstable equilibrium, 

 may in various cases be very different. 



In some cases an alteration in the colour or in the viscosity of the 

 animal may suffice ; in others it requires a change in the digestive or 

 the nervous system, and again in others it becomes necessary to change 

 the existing, or to produce new and additional organs of locomotion, 

 &c. Thus are clearly by nahiral selection produced new forms or 

 types of organisms, designated by naturalist varieties^ species, genera, 

 &c. 



Looking at the same time upon the numerously varied organisation 

 of beings in general, it will readily be understood that the less dif- 

 ferent the organs of a species may be, — that is in other words, the lower 

 its place is in the natural system, — in the same degree would probably 

 decrease the necessit for a change in the organs. In any case, 



