ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 303 



Tunicata. 



Archiascidia neapolitana.* — Oh. Julin gives a detailed description 

 of this interesting new type, the most archaic of known Ascidians, 

 nearest the hypothetical ancestor Protoascidia. It is like the young 

 oozooid of Glavelina in many ways, but it is sexually mature and has no 

 epicardium. On each side of the thorax there are two rows of branchial 

 stigmata, much elongated, separated by a transverse sinus, and arising 

 from two branchial clefts, appearing one behind the other. There is no 

 epicardium, but throughout the length of the abdomen there is a frontal 

 partition of peribranchial origin dividing the abdomen into a larger 

 dorsal and a more restricted ventral sinus. In the nature of the intes- 

 tinal gland, in the structure of the gonads, and in many other ways, 

 Archiascidia is true to its name. A new family Archiascidiida? is 

 required. 



Mesoderm Formation and the Structure of the Tail in Ascidian 

 Larvae .| — -Philipp Heinemann has studied the development of Ciona 

 intestinalis, Glavelina hpadiformis, and Molgula nana, with especial 

 reference to the origin of the mesoderm and the structure of the tail. 

 He agrees with Kowalewsky and Seeliger that endoderm-cells lying 

 laterally below the nerve-cord and the ectoderm give origin to the 

 mesoderm ; he disagrees with the view of Davidoff that an endoderm- 

 cell divides into a mesoderm-cell and another endoderm cell, with the 

 view of Van Beneden and Julin that diverticula from the enteron form 

 the mesoderm primordia, and with one of Castle's conclusions that in 

 the posterior region of the body the mesoderm has an ectodermic origin. 



In the three forms studied the " tail " is composed of similar parts, 

 namely the peripheral fin-fringe, a central notochord, the nerve-cord, 

 the two muscle-bands, and an eudodermic process. 



Dolchinia mirabilis.J — A. Korotneff described more than ten years 

 ago a remarkable Tunicate from Naples which he named Dolchinia 

 mirabilis. In passing through Naples in 1903 he was fortunate enough 

 to find that his discovery had re-occurred in abundance. It had only 

 once been found in the intervening decennium. 



The form in question is a gelatinous and transparent tube almost 

 covered with salpiform individuals fixed to the surface by stalks which 

 are readily detached. In his first specimens Korotneff found only one 

 kind of zooid, but in the second set he found a second type with a 

 marked resemblance to the lateral form of Doliolum. He gives a 

 detailed description, and shows that Dolchinia must be ranked phyleti- 

 callv alongside of Doliolum. 



INVERTEBRATA. 



Mollusca. 



Myocardium in Primitive Molluscs.§ — P. Vigier and Fr. Vies have 

 studied the minute structure of the myocardium in one of the Amphi- 



* MT. Zool. Stat. Neapel, xvi. (1904) pp. 489-552 (1 pi.). 



t Xeitachr. wiss. Zool., lxxix. (1905) pp. 1-72 (4 pis.). 



I MT. Zool. Stat. Neapel, xvi. (1904) pp. 480-8 (1 pi. and 2 figs.). 



§ Comptes Kendus, cxxxix. (1904) pp. I22tj-S. 



