308 



SCIENCE. 



[Vol,. II., No. 31. 



the nervous system, salivary glands, segmental or- 

 gans, etc. 



The vascular system is imperfectly known. Bal- 

 four describes a dorsal tube without apparent muscu- 

 lar walls as the probable representative of the heart, 

 and mentions a less distinct ventral vessel. (Cf. note.) 



The segmental organs, wliich were first recognized 

 by Balfour,^ conform to the structures designated by 

 tlie same name in annelids. They consist of: 1°. a 

 vesicular portion opening to the exterior; 2°.. a coiled 

 portion, wliich is again subdivided into several sec- 

 tions; 3°. a terminal section ending by a somewhat en- 

 larged opening into the lateral compartment of the 

 body-cavity. The first two pairs, corresponding to the 

 fourth and fifth. legs, differ somewhat from the rest, 

 which are all similarly constructed. They are lined 

 by an epithelium, which varies in cliaracter in the 

 different parts of the oi'gans: in the first portion, tlie 

 cells are large, flattened, and have large protuberant 

 nuclei; the second portion lias a columnar epithelium 

 in its outer part, in wliich, further, two regions may 



Fig. 5. Part of segmental organ : o .t, extei 

 eegmentjil oi'gan;v^ terminal portion of duet; v, vesicle 

 7- 9. .9. J.. «ii<-fpflsi\/#i portion!* of segmental canal: ]}/, i 

 ' nortion_ 



, external opening of the 



8 ot, terminal portion. 



eegmentjil , 

 1,2,3,4, L_ 

 nal opening; 



be distinguished histologically; a third region within 

 this outer part has large, flat, granular cells, with 

 disk-like nucleolated nuclei; while a fourtli region,' 

 the innermost of tlie middle portion again, has a lin- 

 ing of small columnar cells. The inner portion has 

 a thick columnar epithelium crowded with oval nuclei, 

 and opens with reflected lips Into the body-cavity. 



The fjeneratioe organs are briefly descril)ed by the 

 ed itors, who do not, however, deal with tlieir histology. 

 The male organs consist of a pair of testes, a pair of 

 prostates, and vasa deferentia and accessory glandular 

 tubules. The female organs C(msist of a median un- 

 paired ovary and a pair of oviducts, wliich are dilated 

 for a great part of their course to perform a uterine 

 function, and whicli open behind into a common ves- 

 tibule communicating directly with tlie exterior. In 

 all the legs except the first tliere are glandular bodies. 

 The large accessory gland opening in the last leg of 

 the' male is probably a modification of one of the 

 scries for which the name ' crural glands ' is proposed- 



Part III., also entirely written by the editors, treats 



1 Balfour: Quart. joum.microsc, 3c.,-sXii,\?rtQ. 



of the development. This contains illustrations, 

 serving to accompany the notice published in the 

 Koyal society's proceedings (Sciknce, i. 453) ; certain 

 requisite explanations are added; then follow descrip- 

 tions and figures of older 

 embryos than had been pre- 

 viously described by Bal- 

 four. Special attention is 

 called to the following more 

 important facts: — 



" 1. The greater part of 

 the mesoblast is developed 

 from the walls of the ar- 

 chenteron. 



"2. The embryonic 

 mouth and anus are derived 

 from the respective ends of 

 the original blastopore, tlie 

 middle part of the blasto- 

 pore closing up. 



"3. The embryonic 

 mouth almost certainly be- 

 comes tlie adult mouth; 

 i.e., the aperture leading 

 from tlie buccal cavity into 

 tlie pharynx, the two being 

 in the same position. The 

 embryonic anus Is in front 

 of the position of the adult 

 anu.s, but in all probability shifts back, and persists 

 as the adult anus. 



"4. The anterior pair of mesoblastic somites give 

 rise to the swellings of the pre-oral lobes aud to the 

 mesoblast of the head.i 



" There is no need for us to enlarge upon the Impor- 

 tance of these facts. Their close bearing upon some 



Fig. 6. Embryo, ' stage C,' 

 witti live somites: a, anal 

 (?) end. The lips of the 

 blastopore have united in 

 the middle. 



Fig 7 Section thiough the open blastopore of the embiyo drawn 

 111 hir 6 bl, blastopoie, mc6, raesodexm, et, ectoderm, eiit, 

 entoderm. 



of tlie most important problems of morphology 'will 

 be apparent to all." 



The paper terminates with a few appropriate and 

 telling quotations from Balfour's ' Comparative em- 

 bryology.' The memoir displays the best qualities 



1 *( ^e have seen nothing in any of our eectio 

 identify as of so>caUed mesenchymatous origin.*' 



i which we can 



