536 SUMMARY OF CURRENT RESEARCHES RELATING TO 



studies have revealed, and to the apparent independence of the repro- 

 ductive life of the species from the somatic life of the individual. 



Propagation of Blood Filariae.* — G. Noe has continued his experi- 

 ments on the mode of propagation of Filaria immitis, and confirms the 

 conclusions which he previously reached along with Prof. Grassi. The 

 experiments were made on dogs, and the results obtained are convincing 

 (veramente brillanti). The parasite passes from one host to another 

 solely by means of the mosquito's puncture after the fashion already 

 indicated, and to suppose any other mode of infection is quite gratuitous^ 



Fixation of Intestinal Parasites.f — Dr. A. Rizzo describes different 

 modes of attachment. In Sclerostomum equinum and Scl. tetracanthum, 

 as in Uncinaria, there is formed, at the point where the worm adheres 

 to the mucous membrane, a special interlocking arrangement — " una clava 

 di aspirazione." There is a papilla round which the buccal capsule fits, 

 and into which the two strong chitinous buccal teeth of Scl. equinum 

 are inserted. The mode of adhesion in Trichocephalus affinis is also 

 described in detail, with special reference to a longitudinal granular 

 striated region near the anterior and on the ventral surface, which has 

 been interpreted as an adhesive organ of copulation, which is, however, 

 more likely adapted to parasitic fixation. 



Platyhelininthes. 



Oogenesis in Thysanozoon brocchi. % — E- Schockaert finds that 

 within the nucleus of the oocyte in this form there appears at a very 

 early stage a non-granular filament, quite distinct from the chromatin 

 thread, which frequently divides transversely to form two threads. The 

 single or double filament elongates and thickens, and ultimately 

 applying itself to a nucleolus, diminishes to form a band surrounding 

 part of the nucleolus, and quits the nucleus. If the filament has 

 divided, then the two filaments with their adjacent nucleoli occur at 

 opposite poles of the nucleus ; if it remains single till this stage, division 

 now occurs, and the two centrosomes are formed. The stage at which 

 division occurs determines whether the centrosome appears single or 

 double from the first. These results should be compared with those of 

 Gerard, to which they are prior. 



Oocyte of Prostheceraeus vittatus. § — 0. Gerard has studied the 

 processes of maturation and fertilisation in this Polyclad. The fol- 

 lowing are among the more striking of his results. The oocyte of the 

 first order contains an oval nucleus with a single nucleolus, which early 

 disappears and appears to feed the nucleus. Within the nucleus there 

 occurs in addition a slender filament, the centrogenic element, possibly 

 of nucleolar origin, more likely formed of nuclein. This filament grows- 

 as the other egg-elements grow, and when the chromatin reaches the 

 skein-stage, divides into two secondary filaments, which travel towards 

 the opposite ends of the nucleus, and then, passing into the cytoplasm,, 

 form the central corpuscles. The central corpuscles seem to increase- 



* Atti (Read.) R. Accad. Lincci, x. (1901) pp. 317-9. 



t Tom. cit., pp. 309-17 (3 figs.). 



% La Cellule, xviii. (1901) pp. 37-137 (4 pis.). 



§ Tom. cit., pp. 141-248 (3 pis.). 



