ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 61 



(MacMunu's enterochlorophyll) of higher Invertebrates ; (2) Anthea- 

 green ; (3) rose and purple-red Floridine ; (4) a (yellow) Uranidine ; 

 (4) chlorophane- and rhodophane-like lipochromes, but in small 

 quantity as in Anemonia ; (6) a red lipochromoid which is not readily 

 dissolved out. 



The extraction and examination of the different pigments are 

 described, and a spectrum table is appended. The colouring matter of 

 the yellow ceils of Anemonia is constantly to be found in stone corals. 

 The most abundant associated pigment is a yellow uranidine which 

 entirely resembles aplysinofulvine. Floridine, which is common in 

 sponges, is also very frequent among corals. The persistent red of the 

 noble coral (Corallum rubrum), and of the organ-pipe coral (Tubipora 

 musica) resembles that of many mollusc shells, and consists of a rhodo- 

 phane pigment combined with the lime. 



Nervous Tracts in Alcyonids.* — Dr. C. F. W. Krukenberg has 

 investigated the nervous physiology of Xenia in order to elucidate the 

 relations of dependence between the individual polyps and the colony. 

 Something has already been done in this direction with Polyzoan 

 colonies, but hardly anything has yet been achieved with Alcyonids. 



By a series of experiments the following facts were established in 

 regard to individual polyps : — (1) conducting nervous strands penetrate 

 the entire body of the polyp, on the sides of the wall as on the basal 

 plate, both in the oral disc and in the tentacles ; (2) stimuli from 

 one half of the body to the other pass more readily via the oral disc 

 tban by means of the strands in the basal plate ; (3) stimuli pass 

 more readily from the base to the mouth-disc than in the opposite 

 direction. 



In regard to the more difficult problem of the relation of the indi- 

 viduals to the general colony, Krukenberg draws the following con- 

 clusions from his experiments : — (1) All portions of the Xenia colony 

 are provided with contractile tissue. The contractions are directly 

 under the influence of a ganglionic network, which is somewhat super- 

 ficially spread out in the branches, the stem, and the foot-plate. (2) The 

 ganglionic network is much more sparsely developed in that portion of 

 the colony which simply supports (the branches, the stem, and the foot- 

 plate) than in the oral disc and tentacles of the polyps. Its influence is 

 especially marked in the stem on such portions as underlie the branches, 

 where there must be larger aggregates of ganglia. This fact seems to 

 explain why influences take effect almost exclusively above the point of 

 irritation, and not backwards from it. (3) Stimulation of a point on 

 the stem is much more readily propagated in the transveise than in the 

 basal direction. Hence may be inferred the existence of cross anasto- 

 moses in the ganglionic network. The relations are very lucidly dis- 

 played in a diagrammatic figure. 



Finally, the author devotes some space to a criticism of certain re- 

 searches of Keller on the contractions of Xenia. The gist of these 

 observations lay in the conclusion that on the peristome, probably 

 on the margin and near the base of the tentacles, motor centres were 

 present which occasioned rhythmic contractions. With the same species 

 {Xenia fuscescens), and at the same locality (Suakim), Krukenberg was 

 quite unable to observe the rhythmic contractions which Keller even 



* Vergl. Physiol. Studien, II. Reihe, 4 Abth. (1887) pp. 59-76 (1 pi.). 



