ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 47 



case was such a termination even unsatisfactorily observed. From a 

 common trunk composed of several fibres one separated and ended at 

 a muscle ; here it divided into two fibrils, which each terminated in a 

 muscular fibre, where it formed a kind of motor plate ; the arrange- 

 ment, therefore, was very similar to that described by Ranvier for the 

 muscles of the stomach, from which it differs only in the somewhat 

 larger size of the plate. 



The Echiurida.* — Professor E. Greef is of opinion that there is 

 no close genetic affinity between the Gephyrea and the Echinodermata, 

 but that the former represents a distinct class allied to the Annelids 

 and divisible into an armed (Echiuridas) and unarmed (Sipunculidse) 

 group. 



In this elaborate monograph he deals, after an historical and 

 a bibliographical introduction, with (1) their distribution, which 

 appears to be very wide, though Bonellia is confined to the Mediter- 

 ranean area, and Echiurus to the northern side of the equator. 

 Their coloration can only be made out in the fresh condition as the 

 pigment is soluble in alcohol. The various organs are dealt with in 

 order ; the presence of a central canal in the nervous system is noted, 

 and it is suggested that it is a remnant of the ectodermal invagina- 

 tion ; fluid is to be found in this canal. A full account is given of 

 the curiously minute male of Bonellia. The essay concludes with a 

 systematic definition of the family, and of the three genera and fifteen 

 species of which it is composed. 



Segmental Organs and Genital Gland of some Sipunculida.j — 

 Dr. C. P. Sluiter discusses the question whether the so-called brown 

 tubes have or have not an opening into the coelom ; after having had 

 the opportunity of examining a number of fresh tropical forms, 

 he has almost always been able to detect an orifice, which, however, 

 was not, as is ordinarily stated, placed near the anterior, but just 

 " beside the posterior end of the tube ; in only one case was the orifice 

 anterior and then there was an infundibular structure developed which 

 communicated by the funnel with the interior of the tube ; the funnel 

 proper consists of four lobes, two larger lateral, and a small dorsal 

 and a small ventral ; about the middle of the funnel the lobes fuse 

 with one another to form the tube. In some few cases the author was 

 unable to observe either an anterior or a posterior orifice ; this was in 

 forms in which the longitudinal musculature was not differentiated ; 

 the wall of these brown tubes is, however, extremely thin, and can be 

 easily ruptured. In structure the walls generally exhibit a circular 

 and a longitudinal layer of muscles, and a series of radial glandular 

 tubes. The author describes the generative organs, and finds that the 

 glands form sausage-shaped structures in a deep groove between the 

 dorsal retractors; these bodies have a wall of fibres of connective 

 tissue which extends and is attached to the wall of the exterior ; the 

 inner side of this wall is invested by a layer of small mother-cells 

 from which egg-cells are regularly given off. In other forms the 



* Nova Acta Acad. Cses. Leop.-Carol. Germ. Nat. Cur., xli, ii. (1880) pp. 1-172 

 (9 pis.). 



t Zool. Anzeig., iv. (1881) pp. 523-7. 



