February 3, 1899.] 



JSCIENCR 



183 



evidence now in our possession, the question 

 could not be definitely settled. 



Mr. p. p. Calveet referred to a recently 

 published paper on the structure of the gizzard 

 of dragon flies and recounted the results of the 

 recorded observations. He had been able to 

 dissect out the gizzard, in good condition for 

 study, from dried specimens, one having been 

 obtained from a fly captured in Burmah in 1889. 

 The ridges, wiiich form a prominent feature of 

 the organ, do not seem to be smoothed away 

 by food, their function being probably that of a 

 sieve. 



Edw. J. Nolan, 

 Recording Secretary. 



ZOOLOGICAL CLUB, UNIVERSITY OF CHICAGO. 

 MEETINGS OF THE AUTUMN QUARTER. 



Polymorphic Nuclei in Embryonic Germ-cells. — 

 While studying the oogenesis of Loligo pealei 

 Les., the squid common at Woods Holl, Mass., 

 I noticed that the embrj'onic germ-cells showed 

 nuclei much lobed and contorted — a condition 

 which has been observed in other germ-cells 

 and variously accounted for as due to amitosis ; 

 to deterioration with accompanying fragmenta- 

 tion, to increase of the assimilating surface, etc. 

 I wish here briefly to call attention to this con- 

 dition in the squid. An account of the oogene- 

 sis will soon be completed. 



Sex first becomes distinct shortly after hatch- 

 ing, the embryonic germ-cells being apparently 

 indifferent. During and for a short time after 

 the embryonic period the genital gland rests 

 upon the left tongue of the internal yolk-lobe. 

 Nourishment is evidently direct througli the 

 yolk-epithelium, the genital blood-vessels de- 

 veloping toward the end of this period. During 

 this time the nuclei of the germ-cells enlarge 

 rapidly and show marked lobes, bays and con- 

 tortions, a centrosome occurring in one bay of 

 each nucleus. Their descendants, the oo- and 

 spermatogonia, also show a polymorphism of 

 the nuclei which becomes less striking as the 

 number of generations increases and the size of 

 the cells decreases. These cells always lie near 

 the blood-vessels of the gland, and their chroma- 

 tin, like that of the parent cells, is never finely 

 divided, but massed in clumps, a large clump 

 lying near each bay of the nucleus. A similar 



though less marked polymorphism exists in 

 nearly all the somatic nuclei at this embryonic 

 period, and is conspicuous in those rapidly pro- 

 liferating stroma-cells at the hilum in which 

 the blood-vessels form. 



This condition of the nuclei in the germ- 

 cells of the squid is due neither to deterioration 

 nor to amitosis, for it is shown by all the germ- 

 cells, which after attaining a large size divide 

 by mitosis, giving rise to the oo- or spermato- 

 gonia. It seems probable that it is here caused 

 by the rapid growth of the nucleus, together 

 with the retention of the centrosome and massed 

 condition of the chromatin in these rapidly 

 dividing embryonic cells. 



Mary M. Sturges. 



Larvx of Arenicola cristata. — The highly 

 resistant organization of these larvse renders 

 them remarkably well fitted for artificial 

 rearing. They may be reared from the egg 

 in sea water kept aerated by Ulva up to a 

 stage where the structure and habits of the 

 adult are practically complete. Addition of 

 carmine powder to the sea water seems to ac- 

 celerate development up to a certain point, 

 probably on account of the increased food sup- 

 ply which is thus furnished to the developing 

 larvae. 



They leave the egg-strings as slightly elon- 

 gated, strongly heliotropic larvEe with two eye- 

 spots and three body segments, each with two 

 pairs of setse. Prototroch and paratroch, to- 

 gether with a median ventral band of cilia, are 

 present, and by their aid the larvae swim about, 

 actively rotating on the long axis at the same 

 time. After a day or two they settle down and 

 begin to form the tubes in the interior of which 

 they undergo the remainder of their develop- 

 ment. These tubes are of very simple construc- 

 tion, being composed of any convenient foreign 

 particles united by a glutinous substance se- 

 creted apparently by certain large clear cells, 

 situated anteriorly, which are to be regarded as 

 gland-cells. From now on development pro- 

 gresses uniformly and growth proceeds as usual 

 by the addition of segments at the posterior 

 end. The opacity resulting from the presence 

 of the yolk gradually diminishes as the yolk 

 becomes absorbed, and when twelve segments 



