650 SUMMARY OF CURRENT RESEARCHES RELATING TO 



boundaries are not apparent. Twenty-five nuclei with their unseg- 

 mented protoplasm constitute the true embryo or oncosphere. The 

 nuclei stain deeply, and are all alike, whereas in Bothriocephalic^ and 

 Cystotamice the oncosphere consists of two kinds of cell, large and 

 small. Three or four cells with very large nuclei form the inner 

 embryonic membrane, and correspond to the mantle-cells of Bothrio- 

 cephalidse. Finally, two cells with large nuclei constitute the outer 

 embryonic membrane, corresponding to the single membrane of the 

 Bothriocephalidae. 



Larva of Caryophyllseus mutabilis.* — Dr. Al. Mrazek has found, in 

 the anterior region of Tubi/ex, a Cesfcode larva, which he believes is 

 certainly that of this form, aud not of ArrJiigetes. The evidence chiefly 

 relied upon is the size (5 mm.) — much greater than that of Archigetes ; 

 the existence of the remarkable cell-strands, described by Will in the 

 adult ; the condition of the reproductive organs ; and the structure of 

 the head. As in Archigetes, an embryonic appendage (tail) is present. 

 In regard to the central cell-strands of Caryojphyllseus, the author is of 

 opinion that these represent a remnant of the primitive digestive organs. 



New British Nemertea. f — R. C. Punnett describes Micrella rufa 

 g. et sp. n., and Oxypolia beaumontiana g. et sp. n., both found at 

 Plymouth. The abbreviated generic diagnoses are as follows : — Micrella, 

 body elongated and slender, without side folds and with caudal appen- 

 dage. Ehynchoccelom to posterior end, and with pockets in oesophageal 

 region. Proboscis two-layered, and with muscle crosses. Excretory 

 system with long duct and a single pair of openings at the posterior 

 end. No neurochord cells. Side organ present just behind excretory 

 pore. The genus is thus seen to be very primitive, the most primitive 

 of the known genera of Liueidaa. In Oxypolia the body is short and 

 stout, and the proboscis pore ventral. There is a circular ciliated groove 

 round the head just in front of the mouth, and the rhynchocceloni reaches 

 to the end of the body. The excretory system has many ducts, and the 

 cerebral organs are small and not surrounded by blood-lacunae. The 

 proboscis has three muscle layers, but is without muscle crosses. The 

 genus appears to occupy an intermediate position between Valencinia 

 and Eupolia. 



Callinera biirgeri. $ — D. Bergendal gives a full description of this 

 aberrant Palaeonemertean, which must be included in Burger's Protone- 

 mertini. Its most important peculiarities, all discussed in detail, may 

 be summarised : — (1) the pointed head, not marked off from the body, 

 with asubterminal proboscis aperture, aud the mouth opening just behind 

 the brain ; (2) the absence of special cerebral organs and the presence 

 of contractile lateral organs ; (3) the strong development of the brain, 

 especially of the dorsal ganglia, whose fibrillar nuclei, widely extended, 

 lie directly on the Grundschicht, and the shortness of the ventral 

 cerebral commissure ; (4) the development, restricted to the head, of a 

 strong nervous layer; (5) the unpaired oesophageal nerve; (6) the 



* Ceutralbl. Bakt., 1" Abt., xxix. (1901) pp. 485-91 (3 figs.). 

 t Quart. Journ. Micr. Sci., xliv. (1901) pp. 517-01 (2 pis.). 



t Lunds Univ. Arsskft., xxxvi. (1900) pp. ]-47 '.111(1 vii. (2 pis. and 25 figs.); and 

 xxxvii. (1901) pp. 49-118. 



