92 SUMMARY OF CURRENT RESEARCHES RELATING TO 



mode of formation of the genital products are in the Priapulidae so different 

 from what is seen in other Gephyrea, that they afford another reason for 

 that rearrangement of the system of the class to which Hatschek has already 

 directed attention. 



lymphatic System in Enchytraeidae.*— Dr. W.Michaelsen corroborates 

 and extends what he has previously noted in the Chtetopod Enchytraeidae 

 as to the existence of vessels connecting the gut and the circulatory system. 

 After giving diagnoses of Buchholzia and Enchitrseus tenuis, he describes in 

 detail the position of these connecting vessels. Between the intestinal 

 epithelium and the circular muscles there is a blood-sinus divided into 

 numerous intertwining and communicating canals. Between certain seg- 

 ments a system of fine canals can be detected penetrating the epithelium- 

 cells — these are the chyle- vessels. The chyle passes into these, and thence 

 by osmosis into the blood. Dr. Michaelsen describes analogous arrange- 

 ments in various forms. The appendage to the gut in Brada is regarded 

 as morphologically between the appendage in Buchholzia appendiculata and 

 the " heart-body " of many Annelids. The former is lymphatic, the latter 

 probably elfects the purification of the blood, while the appendage of Brada 

 is perhaps also physiologically between the two, serving both for the 

 absorption of the nutritive juice and the separation of the useless com- 

 ponents. 



Oogenesis in Ascaris.f — The phenomena of maturation in the ova of 

 Asca/ is megalocejjhala, so recently investigated by Nussbaum and by van 

 Beueden, have now been observed by Prof. J. B. Carnoy. As the two 

 former authorities diff'ered, so Carnoy from both. The memoir is very 

 handsomely got up — quite an edition de luxe, with its large print, wide 

 margins, tabular summaries, and magnificent plates. 



Carney's principal observations are thus summed up. In Ascaris mega- 

 loce-phala, (a) the typical nuclein element divides early into eight approxi- 

 mately equal stumps, which separate immediately into two groups of four, 

 disposed laterally with respect to the axis of the future spindle, and 

 forming the two germinal spots, (h) These are motionless during sub- 

 sequent development and maturation, (o) At the entrance of the sperm, 

 sometimes sooner, sometimes later, the germinal vesicle begins to move, 

 and bursts its membrane ; a karyokinetic figure appears with a halved 

 sjiindle and with associated asters of various orders and degrees of com- 

 plexity. The germinal spots remain equatorially, each on half a spindle, 

 without change or division, [d) At the surface the figure dislocates and 

 divides, or remains intact, and disappears into ordinary cytoplasm, in which 

 the two germinal spots remain still intact. (e) Between the latter a new 

 spindle appears, the spindle of separation, and at the same time the small 

 rods often arrange themselves in a row. (/) Soon one of the spots is ex- 

 pelled with a variable portion of protoplasm, but without undergoing 

 change ; the other half remains also as it was. (</) From the latter a 

 second figure arises, separated into two grou})S just as at first. These lie 

 equatorially, and do not undergo fragmentation or any change, (/t) The 

 new figures are exactly like the old, halved up the middle, much elongated, 

 and rich in asters. They too are resolved into ordinary cytoplasm. A 

 new separation spindle appears, and one of the two groups is expelled. 

 The survivor forms, of course, the final nucleus, and becomes provided with 

 caryoplasma and a membrane. The memoir also contains a large number 

 of more general notes on the problem of division. 



♦ Arch. f. Mikr. Anat., xxviii. (1886) pp. 292-304 (1 pi.). 

 t La Ctllule, ii. (188G) pp. 1-77 (4 pis.). 



