442 SUMMARY OF CITHUENT RESEARCHES RELATING TO 



Notes on Young Enteropneusta.* — W. E. Ritter and B. M. Davis 

 give an account of a number of interesting features in the development 

 ;ind habits of Tornaria ritteri and others. Diminution of size marks 

 the metamorphic period during which both retrogressive and progressive 

 changes are baking place. It appears that the difference in size and 

 form assumed by the larva at different times in its career is more a ques- 

 tion of the distribution of a nearly constant quantity of body substance 

 than of the addition and distribution of new substance. Their researches 

 have strengthened the suggestion of a general functional similarity 

 between the oesophageal ciliated band previously described by Ritter 

 and the prochordate endostyle, although the question of true homology 

 remains as doubtful as ever. The vital activities of this animal are at 

 a very low level ; food-taking seems to be wholly wanting for a large 

 part of the larval period ; respiration and excretion are on the simple 

 protoplasmic level ; responses to stimuli are detected only with difficulty ; 

 body movements are effected exclusively by cilia. The eggs are deposited 

 on the sea bottom, while the larva? are pelagic. The larvae rise by a 

 reduction of their specific gravity and by the action of their cilia. They 

 swim upward in a spiral manner. Tornaria appear to react but slightly 

 if at all to light of normal intensity. Particulars of a new species, 

 Tornaria hvbbardi, are given, and some notes on the direct development 

 of DoJichogJossus pusillus Ritter. 



Germ-Cells in Pedicellina americana.t — L. I. Dublin has studied 

 the history of the chromatin of the germ-cells, and finds that oogenesis 

 and spermatogenesis are in general identical processes. The normal 

 number of chromosomes is probably twenty-two, and full details of the 

 maturation divisions are given. The eggs are fertilised internally, and 

 the pronuclei do not unite intimately ; the chromosomes are very early 

 re-formed and give rise to twenty-two V's of the first somatic mitosis ; 

 they split longitudinally and preserve this form up to the last sperma- 

 togonial and very probably oogonial generation, where they are converted 

 into dumb-bell shaped rods. The egg nucleolus appears early during 

 the oocytic growth-period, and increases in size at the expense of the 

 cleavage products of the chromatin ; later it becomes vacuolated, stains 

 throughout as a plastin body, and with the approach of the first matura- 

 tion division disintegrates, the remains being cast out as a meta- 

 nucleolus. 



Echinoderma. 



Variability and Autotomy of Phataria.J — Sarah P. Monks dis- 

 cusses Phataria (Linckia) vnifascialis Gray, var. bifascialis, a starfish 

 remarkable for the variability in the size and number of its rays. 

 Regularity is the exception. In over 400 specimens, not more than four 

 were symmetrical, and no two were alike. 



The breaking is automatic, and is effected by pulling apart or frac- 

 ture without strain ; there is co-ordination of parts in producing the 

 separation ; the tissues relax at the plane of rupture ; this plane may be 



• Univ. California Publications, i. (1904) pp. 171-210 (8 pis.), 

 t Aimals N.Y. Ac-ad. Sei., xvi. (1905) pp. 1-64. 



* Proc. Acad. Sci. Philadelphia, 1904, pp. 596-600 (1 pi.). 



