194 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Systematic Position of Balanoglossus.* — Professor A. Giard 

 has some observations on the paper of Metschnikoflfj on this form, in 

 which he points out that the presence in its larva, Tornaria, of a 

 very special heart (which he has never observed in the larvae of any 

 Echinoderm), the relatively late appearance of the ciliated circlets, 

 and the existence of a muscular band uniting the aquiferous system to 

 the median point of the eye-spots, all present difficulties which 

 prevent us from at once accepting the view of the close relationship 

 of the Enteropneusti and the Echinodermata. 



Attention is directed to one point of similarity ; four years ago 

 the author showed that, in the Echinoidea, after the reproductive period 

 has passed, the genital glands form culs-de-sac filled with very large 

 elements which have no resemblance to generative cells, and have 

 within them a large vacuole, which owes its appearance to the 

 atrophy of the nucleus ; in addition, there are in the cell small 

 brownish concretions, similar to those found in the renal organs of 

 numerous Invertebrates ; deutojilasmic elements which are, later on, 

 absorbed by the developing genital cells, and a large number of 

 crystals of phosphate of calcium are also present. From these 

 observations the author concluded that, for a certain part of the year, 

 the genital glands of Echinoids took on an excretory and a deuto- 

 plasmigenous function. A renewed study of Kowalevsky's memoir 

 on Balanoglossus, showed the author that a very similar state of 

 things was to be observed in that animal, but he here insists that it 

 would be rash to give too much value to a morphological similarity 

 which may be simply due to a similarity of function. A fair objec- 

 tion would be raised by any one who should point out that nothing 

 of the kind is to be observed in the Starfishes. At the same time, 

 the absence of segmental organs in Balanoglossus would seem to be 

 very significant. If we distinguish the excretory apparatus of the 

 Invertebrata as (a) protonephridia, e. g. the organs of Turbellaria, 

 Cestodes, Trematodes, Rotifers, &c., and (/3) the deutonephridia, or 

 segmental organs properly so called, we find that we cannot place 

 with the former either the water system of Echinoderms, or that of 

 Balanoglossus ; nor are they homologous with the modified deuto- 

 nephridia. 



The relationship of Balanoglossus to the Tunicata is absolutely 

 denied, the resemblances between them being regarded as purely 

 analogous ; provisionally, therefore, Giard accepts the general doctrine 

 of Metschnikoff, without pretending to exactly define the genealogical 

 position of this curious and interesting form. 



Nervous System of Platyhelminthes.l — Of the fourth and fifth 

 parts of Dr. A. Lang's contributions, the most important point is the 

 discussion of the character of the nervous system as treated compara- 

 tively. Comparing them with the Ctenophora, the only group of the 

 Coelenterata which have a corresponding histological and anatomical 

 differentiation of the germinal layers, the author points out that in 



* Bull. Sci. Dep. Nord, iv. (1881) pp. 372-8. 



t See this Journal, 1. (1881) p. 462. 



X MT. Zool. Stat. Neapel, iii. (1881) pp. 53-96 (2 pis.). 



