42 SUMMAllY OF CURRENT RESEARCHES RELATING TO 



layer in the embryonic sac fui'nislies the nutriment for the first 

 six blastomeres; these then proliferate, and give rise to small 

 lecithal cells ; segmentation is unequal, and division alternates with 

 gemmation ; the lecithal cells form a peripheral layer to the morula, 

 and also extend inwards between some of the blastomeres ; growing 

 rapidly, they at last surround each of the fourteen blastomeres ; they 

 then penetrate into the blastomeres themselves, and those that do 

 so disappear. At a later stage the blastomeres become broken up 

 into small protoplasmic cells, which are only distinguished from the 

 nutrient ones by the characters of the protoplasm ; they soon increase 

 greatly in size, and again increase by gemmation. Meanwhile changes 

 are being effected in the sac, and we get in time to an embryo which, 

 larger in size, rounded in form, and placed in the uterus, begins to be 

 differentiated into its separate parts; the primitive intestine, the 

 blastoccel, and the amnios are set up, and then the embryonic and 

 blastodermic membranes begin to be developed. The essential parts 

 of all the subsequent changes not here described in detail are stated 

 to lie in the multiplication of the segmentation cells, and in the 

 absorption of the lecithal cells, which serve to nourish them ; on the 

 ruins, as it were, of those latter the segmentation cells give rise to 

 embryos ; first of all, to the solitary, and then to the compound Salpa ; 

 in other words, there is a metamorphosis, and the details of the rela- 

 tions of the proembryo to the true embryos differ in different species, 

 on the comparative study of which the author promises to enter on 

 another occasion. 



Compound Ascidians of the Bay of Naples.* — A paper on the 

 anatomy and development of these animals by Dr. A. Delia Valle is 

 reported on by MM. Trinchese and De Sanctis. In the genus 

 Distaplia Delia Valle,| the colony is either sessile or pedunculate ; 

 the individuals are arranged in ramified masses resembling the 

 Didemnidce. The branchial sac has four series of openings; the 

 stomachal walls are smooth; the heart is placed at the apex of 

 the curve of the intestine ; the sexual glands lie on the right side, 

 somewhat above the heart ; the testis is developed before the ovary 

 and simultaneously in all the members of a colony, so that the 

 colonies are always found either exclusively male or female. The 

 mature ova are collected in the cloaca, whence they fall into a special 

 diverticulum, which developes at this time and is subsequently 

 detached from the animal. The larvae are gigantic and produce 

 buds ; these are formed by a bending outwards of the external wall 

 of the peritoneal sac, not far from the end of the endostyle ; the bud 

 soon separates from the individual which produced it and wanders 

 towards the circumference of the colony, dividing by fission, and thus 

 adding new individuals to the colony. Delia Valle, dealing with the 

 tail of the larva, finds by transverse sections that the axis consists of 

 a cylindrical canal filled with a transparent liquid, which is perhaps 



* Atti Accad. Liacei (Rome) Trans., vi. (1881) pp. 14-5. 



t See this Journal, ii. (1882) p. 768, where an account of a paper on this 

 genus is given from the author's description, differing somewhat from the 

 present one. 



