364: SUMMARY OF CURRENT RESEARCHES RELATING TO 



the vascular trimks which are developed do not, in their present 

 relations, appear to have a physiological significance. It is important to 

 note that the vascular trunks anl lymphatic spaces are continuous ; the 

 author gives some notes descriptive of several of the blood-vessels. The 

 question how, and indeed whether, the blood circulates has not yet been 

 satisfactorily answered. It is probable that the present branchial 

 apparatus has been modified, as compared with an earlier stage in whicli 

 the blood-vessels placed a more important part. 



Below the epithelium of the endostyle, or median ventral tract of 

 the pharynx, there is a chitinous plate which has never yet been 

 described" ; it consists of right and left halves, and is segmented. Prof. 

 Lankester doubts the existence of the muscular tissue which has been 

 described by Schneider in the region of the endostyle. 



The atrio-coelomic funnels or brown canals discovered by the author 

 fifteen years ago have not been described or discussed by any other subse- 

 quent writer, with the exception of Mr. Batvson. It is impossible at present 

 to assign definite physiological characters to these tubes ; their morpho- 

 logical marks are that they are paired short tubes which put the coelom 

 in continuity with the exterior ; so far they resemble the abdominal 

 pores of certain craniate \' ertebrates ; Bateson has shown that they 

 correspond in some pi)ints to the collar-pores of Balanoglossus. Whether 

 all these three structures are modified nephridia remains to be seen ; at 

 the present moment our conceptions of the nephridium are themselves 

 undergoing development and extension. Further observations are 

 needed on the later development of AmpMoxus. 



In conclusion, the author has some remarks on the connective tissues, 

 which, like other tissues ()f this animal, differ very greatly from the 

 corresponding placed tissues in other Vertebrates, and do not closely 

 resemble tho-e of any other animal. The structural varieties of the 

 connective tissue are lamellar, gelatinous, and carbilaginoid. 



Spermatogenesis.* — Signor E. Verson finds that Bomhyx mori offers 

 excellent material for a study of spermatogenesis. In each division of 

 the gonad there is but one large germinal cell, from which all the 

 organized structures, of which the contents of the division consist, 

 gradually take their origin. Its gigantic protoplasmic body gives off 

 peripheral rays in the form of finely branched arms, and contains, in 

 addition to its large vesicular nucleus, with nucleoli, well-characterized 

 granules which are imbedded in the protoplasm of the radiating arms, 

 and are always more numerous near the centre. Later on the granules 

 separate themselves from the radial processes of the germinal cell, and 

 appear to be independent and surrounded by a thin area of protoplasm. 

 They are succeeded by rounded or more irregular protoplasmic masses 

 which contain a number of nuclei. There are also larger almost 

 spherical masses which are much clearer and are definitely limited at 

 their periphery by a circular contour ; their nuclei are also clear, 

 become vesicular, and inclose highly refractive, sharply limited cor- 

 puscles, which, in profile, have the form of a comma or a horse- shoe. 

 In addition to these there are still larger vesicles in which an enveloping 

 layer can be d'stinguished from the contents; the latter contains a large 

 number of nuclei, while here and there a delicate surrounding layer of 

 protoplasm can be made out ; the central space appears to be free from 



* Zool. Anzeig., xii. (1889) pp. 100-2. 



