764 SUMMARY OF CURRENT RESEARCHES RELATING TO 



New Type of Dimorphism found in Antipatharia.*— Mr. G. Brook 

 reports that a study of the ' Challenger ' collection of Antipatharia has 

 shown that some of the genera are dimorphic, while others are not. In 

 AntipatJies the zooids are of the normal sextentaculate type, but show a 

 tendency to become elongated in the transverse axis ; in Parantipathes 

 the transverse mesenteries become enormously elongated, so that the 

 length in the transverse axis is three or four times that in the sagittal ; 

 this elongation has the effect of carrying the " lateral " tentacles further 

 away from the stomod^eum, so that they now appear as three pairs some 

 distance apart ; in P. larix the peristome becomes somewhat depressed 

 on each side of the oral prominence, so that the zooid presents indications 

 of a division into three lobes: one central, containing the stomodteum 

 and the proximal ends of all the mesenteries, and two lateral, which 

 contain the greater part of the transverse mesenteries ; it must be re- 

 membered that the reproductive elements are borne on the transverse 

 mesenteries only, and in Parantipatlws they are confined to such portions 

 as are situated within the lateral lobes. In Schizopathes the three lobes 

 of the zooid become separated from each other by a further depression 

 in the peristome and by the formatinn of a mesogloeal septum; each 

 lobe of the primitively simple zooid thus becomes separated from its 

 neighbour, and in Schizopathes may be considered as dimorphic forms. 

 The middle one, which contains the stomod^um, may be called the 

 gastrozooid, while the lateral, which contain the two reproductive organs, 

 may be distinguished as gonozooids. In BathypatJies the differentiation 

 is carried a step further, for the individual zooids are separated from 

 one another by considerable intervals, though still connected together 

 by axial prolongat ons of their coelentera. 



The author proposes to divide the Antipathidse into the two sub- 

 families of the Antipathinse and the Schizopathinee ; Parantipathes, which 

 is placed in the former, being the link between them. This is the first 

 observed case of dimorphism of this kind in the Zoantharia generally, 

 and is, further, of interest, as being brought about by the division of one 

 zooid into three, and not by a siDCcialization of different individuals ; it 

 differs, therefore, essentially from the dimorphism of Madrepora Purvillei, 

 or that of Hydroids. 



Organization and Phylogeny of Siphonophora.f— -Prof. C. Claus 

 has a somewhat severe review of " E. Haeckel's so-called Medusome- 

 theory." | He points out that eleven years ago he showed that the 

 Medusa-theory and the Hydroid-theory are not as irreconcilably opposed 

 to one another as Haeckel asserts ; this statement is supported by various 

 quotations. It is urged that the Medusome-thtory is a new variety of 

 the Medusa-theory, but it loses probability in the same degree that 

 Haeckel's new special assumj)tion appears arbitrary and unfounded. 

 The proposed new classification, the basis of which is the assumption of 

 a special stem-form for the Discoideee, which may be easily and naturally 

 derived from the Pbysophoridse, will have to be rejected as a novelty by 

 no means justified by the state of the case. Prof. Claus raises similar 

 objections to the many new names proposed and to the new nomenclature 

 for the parts and appendages of the Siphonophora. He thinks that the 



* Proc, R. Sec. Ediub., xv. (lSSS-9) pp. 78-83. 

 t Ann. and Mag. Nat. Hist., iv. (188'J) pp. 185-98, 

 : This Journal, 1888, p. 741. 



