TRANSACTIONS OF THE SECTIONS. 173 



tion most characteristic of the species — the Orthomorphic, or that marked by such 

 typical organization — and the Gamomorphic, or that of the development of the 

 reproductive organs. In any one of these stages we may have a process of gemma- 

 tion interpolated. The results contrast, especially as it occurs in the first and last. 

 As examples of the first, may be mentioned the Trematode and Cystic Entozoa in the 

 animal kingdom, and the Mosses among plants ; in all of which certain provisional 

 forms are interposed between the ovum and the embryonic rudiment of the typical 

 form. The Polypifera and Cestoidea among animals, on the other hand, and the 

 Ferns among vegetables, furnish illustrations of alternation dependent on gemmation 

 in the Gamomorphic stage, and arising from the reproductive organs acquiring the 

 characters of detached and often highly organized structures, comparable to inde- 

 pendent animals or plants. The hood-eyed Medusa; become in this way much more 

 conspicuous organisms than the polype-stock, whose organs they really are. The 

 Cestoidea are remarkable as presenting instances of a double alternation, from a pro- 

 cess of gemmation occurring both in the Cystic or Protomorphic, and in the Tienioid 

 or Gamomorphic stages. 



The succession of forms among the Aphides appear referable rather to an early 

 phase of the typical or Orthomorphic stage. Another remarkable feature of this case 

 is the extent to which the pullulation of gemmre of the same general character is 

 carried — amounting frequently to nine or ten in succession. A like continued pullu- 

 lation to a less extent may take place in either of the other stages, but it is most 

 common in the Orthomorphic, and generally occurs in connexion with cohesion of the 

 gemma?, so as to give rise to those arborescent forms characteristic of the Polyzoa 

 and Polypifera among animals, and of the whole vegetable kingdom. 



A parallelism may be indicated between the phenomena of alternation and certain 

 points in the embryogeny of the higher animals, and in the maturation of the repro- 

 ductive organs. The formation of double monsters in the higher animals, the normal 

 twin embryo of the Polyzoa, the variable number of Taenia- heads budded off by the 

 Cystic Entozoa, and the phenomena of development among the Echinodermata, present 

 us with indications of a gradual transition from the implantation of the embryo on the 

 germ-mass of the ordinary ovum, to cases of well-marked alternation. The repro- 

 ductive process, on the other hand, in the Polyzoa and Hydraform Polypes, in the 

 Salpse and in some Annelides, and the phenomena of impregnation in the Conifers 

 among vegetables, furnish illustrations of a similar transition from the development 

 of the normal reproductive organs, to the formation of conspicuous sexual zooids. 

 In proof of distinctions founded on the comj)lexity of the structures themselves not 

 being of essential importance, reference may be made to the males of the Rotifera 

 and Cirrhipedes, which, though animals with an individuality entirely distinct even 

 from the ovum, are much more defective in organization than some of the sexual 

 zooids now referred to, such as the hood-eyed Medusae. The like accidental nature 

 of the character of isolation, or independent vitality, may be inferred from the 

 power of dismemberment possessed by some of the lower forms of organization, 

 and from the persistence of a certain proper life in particular regions, even of those 

 higher in the scale, as for instance, in the hairs and teeth of mammalia. 



[The paper was illustrated by tabular views of the relations referred to.] 



On the Method of Production of Sound by a Species ofNotonecta. 

 By Peter Redfern, M.D. Lond. 

 During the summer months of the year 1858, the author kept a number of small 

 beetles in an aquarium with other objects. Amongst the beetles was a small 

 Nolonecta with exquisitely marked wing-cases. Not many days had elapsed when 

 a peculiar chirping noise was heard now and then during the day, but much more 

 frequently and continuously in the evening between nine and twelve o'clock. The 

 sound resembled the imperfect pronunciation of the letters cheiv three times in suc- 

 cession. It was heard repeatedly at short intervals for a while, and then, after a 

 much longer pause than before, it was reproduced. At first it gave rise to the idea 

 that a cricket had got into the house, though the sound was not like that produced 

 by this insect. It was then noticed that the sound was most distinct in the neigh- 

 bourhood of the aquarium, and that during its production one particular Notonecta 

 was invariably engaged in the same occupation, viz. that of rubbing its fore-legs 



