I. Morphological and Physiological Works of a General Character. 



I. Morphological and Physiological Works of a General Character. 



Pfeffer points out that Echinoderma is a more correct form of the plural of 

 Echinodermon than Echinodermata and should be used instead of the latter as 

 the group name. 



Hartog suggests that the madreporic system of Echinoderms is both mor- 

 phologically and ontogenetically a left nephridium. He describes experiments on 

 Echinus and Asterias which tend to prove that the ciliary currents set outwards 

 through the madreporite , and not inwards as generally supposed. Observations 

 on the water-pores of Antedon gave similar results , which tend to indicate their 

 excretory function. The connection of the madreporite of most Holothuriaus with 

 the coelom is probably due to the respiratory trees assuming nephridial functions. 

 A free admission of water into the perivisceral and ambulacral systems of an 

 Echinoderm is unnecessary, as all that is wanted can enter by osmosis. 



Hamann ( ] ) thinks that the relationships of the Echinoderms are to be 

 sought for among the worms , more especially the Annelids , to which they are 

 allied both in the structure of the body wall and in the characters of the nervous 

 system. In the latter respect the Asterids with their ectodermal nervous system 

 seem to be nearest the ancestral form ; while in the Urchins the nerve bands have 

 sunk into the mesoderm, carrying with them the superficial epithelium, and there 

 are indications of a degenerate eye -spot. Furthermore the radial schizocoel 

 spaces are not traversed by septa containing blood lacunae as in the Asterids, 

 though there is an oral lacunar ring, situated, however, on the lantern instead of 

 round the mouth. The musculature of the body wall of starfishes has mostly dis- 

 appeared in the Urchins, except for the slight indications of it on the dorsal surface 

 of Spatangids. Summing up our present knowledge about the blood-contain- 

 ing cavities in Echinoderms, H. points out that blood may be found in two 

 different systems of schizocoel spaces, which are well separated in Asterids, but 

 more united in other groups; either of them may be in relation with the lacunar 

 systems of the digestive tube. 



Hamann ( 3 ) describes the genital tubes of Echinozoa and Crinoids as con- 

 taining amoeboid germ cells which wander into the ovaries or testes and there 

 mature into ova or sperm-cells. The genital canal of a Crinoid arm is a perihae- 

 mal space or schizocoel; the genital cord within it consists of a blood lacuna 

 surrounding a genital tube, as described by Ludwig. But the cells lining this tube 

 are not fixed epithelium cells ; for they are amoeboid and wander into the pin- 

 nules where they are nourished by the blood around them and multiply. The 

 aboral blood-vascular ring of Ophiurids, of which Kb'hler could find no 

 trace, is a lacunar space enclosed in a schizocoel and situated just as described 

 by Ludwig [see Bericht for 1880 I p 261]; i. e. it is dorsal in the radii and ven- 

 tral in the interradii , and in one radius it communicates by a short tube with the 

 blood-lacunae in the wall of the stomach. It contains a genital cord lined by 

 germ cells which are amoeboid during life. At the sides of each genital bursa buds 

 grow out from this genital tube into the coelom pushing the epithelium before 

 them , owing to a continual inward movement of the wandering germ cells ; and 

 these buds develop into the isolated ovary- or testis-tubes. The cellular tube 

 within the anal blood-ring of Asterids which Hamann formerly described as 

 excretory in character is now regarded by him in accordance with Vogt & 

 Yung as a genital tube [see Bericht for 1885 I p 189; 1886 Ech. p 9]. Five 

 pairs of branches pass from it along the five interradial septa ; and in young 

 individuals the ends of these form large swellings filled with germ-cells, derived 



