392 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Rhopalodina lageniformis.* — Prof. H. Ludwig has made a renewed 

 investigation of this interesting Holothurian. Some corrections in the 

 descriptions of previous writers are made. A piece from the middle of 

 the stalk-like portion of the body was cut into a series of fine transverse 

 sections ; in these the fine water- vessel and the radial nerve were found 

 lying outside each of the ten muscles ; the oesophagus was only attached 

 by the mesentery inclosing the genital duct, while the rectum was 

 fastened by a number of radial bands, in which were found proportionately 

 large round cells. The five muscles seen in section around the rectum 

 were all of the same size, but of the five around the oesophagus the two 

 which lay nearest to the genital duct — and which, therefore, were, in com- 

 parison with those of other Holothurians, the two dorsal — were much 

 thicker than the other three. The five circular muscles of the body-wall 

 in the region of the oesophagus were continued to the partition which 

 S3parates this part from the region of the rectum ; this character seems 

 to show that the " stalk " of Bhopalodina owes its origin to the fusion of 

 an oral and an anal stalk-like and narrower portion of the body. The 

 connection of the oesophagus with the rectum by radial septa, as described 

 by Semper, does not exist, for the part of the coelom surrounding the one 

 is separated from that round the other by a partition which traverses 

 the whole length of the stalk-like portion of the body ; this partition is 

 clearly the remnant of the median dorsal interambulacrum, by the 

 shortening of which the oral and anal ends of the body have become so 

 closely approximated. 



The five pairs of radial papillae at the anal calcareous ring are really 

 hollow internally, and seem to be nothing more than the anal ends of 

 the radial water-vessels ; a single layer of small, branched, and closely 

 packed calcareous corpuscles is found in their walls. The five pairs of 

 radial papillae form forks of five simple, radially-placed, hollow papilla3, 

 the walls of which present continuous calcifications. The interradial 

 tips of the anal calcareous ring are solid. This ring does not, as Semper 

 thought, consist of five radials and five interradials, but of five calcified, 

 hollow, and bifurcate radial papillae, which are surrounded by a circlet 

 of interradial and radial calcareous plates. 



Monstrous LarvsB of Echinus.t — MM. G. Pouchet and Chabry have 

 made some experiments on the production of monstrous larvae of Echini 

 effected by deprivation of carbonate of lime. They have started from 

 the doctrine of Chevreul that the morphological characters of living 

 beings are, to a certain extent, the function of their chemical constitution. 

 Their experiments were made by rearing larvas in water which had been 

 deprived of the greater part of its chalk by oxalate of soda. As they 

 expected, they found that the spicular substance can be totally sup- 

 pressed by depriving the organism of one of its constituents. Morpho- 

 logical deviation is more marked in proportion as a greater quantity of 

 carbf n ite of lime is removed from the sea- water. 



In water which retained more then one-tenth of its chalk, the larvae 

 were at the sixtieth hour still in the gastrula-stage, while the control 

 larvae bad ramified spicules and a complete intestine. After ninety 

 hours, the former larvae, without developing spicules, passed into a true 

 pluteus-stage, characterized by the difi'erentiation of the intestine into 



* Zeitschr. f. Wiss. Zool., xlviii. (1889) pp. 60-6 (1 pL). 

 t Comptes Rendus, cviii. (1889) pp. 196-8. 



