ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 55 



by Claparede in the anterior somites of tubicolous annelids. The 

 various orifices of communication between the oviduct and the female 

 gland, which Grassi has described in other Chsetognaths, do not 

 appear to be present in this form. The products also escape to the 

 exterior by a ventral, and not by lateral orifices. 



The male gland has the nucleus of its epithelial cells very distinct ; 

 outside the epithelial there is a structureless layer, and beyond this 

 are longitudinal muscular fibres. Some of the epithelial cells of the 

 efferent duct are cylindrical, small, and nucleated, while others, which 

 have no nucleus and are larger and more highly refractive, appear to 

 be glandular in function. 



New Forms of Thalassema.* — K. Lampert describes as new 

 Thalassema formulosum, caudex, sorhillans, and vegrande. He separates 

 the species of the genus into two groups, according as the longitudinal 

 layer of muscles is or is not separated into bundles. The next point of 

 distinction is to be found in the number of the segmental organs, which, 

 as is well known, is not constant in this genus, some species in each 

 division having two, and some three pairs ; this, however, is not an 

 invariable character as in some examples only one pair are developed ; 

 nor can the distinction be of much aid to the systematic zoologist, in- 

 asmuch as the condition of the organs varies much with the maturity 

 of the genital products, for which these glands act as efferent ducts. 



Spermatogenesis in the Nemertinea.f — A. Sabatier believes that 

 the difficulties in the way of observation of the various stages in 

 spermatogenesis are the cause of the different accounts given by 

 various observers, equally well skilled. Many of these difficulties are 

 avoided by the study of the small Tetrastemma flavida, which under 

 the compressorium becomes eo transparent that it is possible to study 

 what is going on in its tissues and organs, even with the aid of high 

 powers ; no previous preparation, nor any reagents are necessary for 

 the examination of its germinal sacs or pouches, which, moreover, are 

 well adapted for the purpose, inasmuch as they are not all at the same 

 stage in development. 



The spermatic sacs of a young Tetrastemma have a pyriform shape, 

 and later on become oval, owing to the pressure exerted on them by 

 the adjoining organs ; they are placed between the internal muscular 

 layer and the csecal diverticula of the intestine, and are formed by a 

 special membrane which is attached by short tubes to the body-wall ; 

 and these open to the exterior by lateral pores. These sacs may be 

 seen to be filled with a finely striated substance, made up of bundles 

 set along various axes ; these bundles vary greatly in size ; they are 

 fusiform in shape ; the median portion forms a zone of varying width 

 and has its contents more or less granular, while the two terminal 

 cones are distinctly striated. If we compress the animal and force 

 the contents out of the sac there escape bundles which are either com- 

 pact, or, when more mature, are broken up into an innumerable quan- 

 tity of spermatozoa. The head of the spermatozoon is cylindrical and 



* Zeitschr. f. Wiss. Zool., xxxix. (1883) pp. 334-42. 



t Mem. Acad. Sci. Montpellier, x. (1882) pp. 385-400 (3 pis.). 



