October 27, 19 10] 



NATURE 



549 



left for the entry of the microgamete. One microgamete 

 only fuses with the macrogamete, and then the oocyst wall 

 is completed by closure of the micropyle. This series of 

 changes, from infection to the formation of oocysts, ex- 

 tends over about eight or ten days in the grouse. At 

 first the oocysts are uninucleate, and their contents com- 

 pletely fill them ; later the contents concentrate into a 

 spherical mass, the nucleus divides into four, around each 

 of which the protoplasm aggregates, forming four round 

 sporoblasts. Each sporoblast develops into an oval 

 sporocyst. in which two sporozoites are formed. The 

 oocysts, when dropped, are very hardy ; some which had 

 been taken from a moor a year previously were found to 

 be still alive. 



Coccidiosis is accompanied by an increase in the number 

 of polymorphonuclear leucocytes in the blood of the host, 

 together with a decrease in the number of the erythrocytes. 

 Young birds are much more susceptible to coccidiosis than 

 older ones, but older birds which have become " chronics " 

 serve as reservoirs of oocysts, and are constant sources of 

 infection. Lime dressing of the soil, which destroys 

 oocysts, is the most effective treatment at present known 

 for combating coccidiosis. 



The Formation and Arrangement of the Opercular 

 Chaetae of Sabellaria. 



Mr. .Arnold T. Watson contributed an account of the 

 opercular chietae of SabeUaria alveolata. The operculum, 

 with which this tube-building polychrete defends the open- 

 ing of its tube, consists of two crescent-shaped structures, 

 each of which is composed of three concentric rows of 

 palese, of characteristic form, borne at the distal extremity 

 of the peristomial lobe. \'iewed from above, the exposed 

 portions of the paleae of the outer and middle rows are 

 seen to be arranged in an imbricated manner, their free 

 ends directed outwards, while the free ends of the palea; 

 of the innermost row, the chstae of which alternate in 

 position with those of the middle row, are directed inwards 

 and upwards. Mr. Watson has found that there are two 



nests " for the formation of the chfetae, an outer one 

 supplying the outer pale£E and an inner one producing the 

 middle and inner paleas, which are packed alternately in 

 the nest. The chaetae can be traced, and evidently travel, 

 in a somewhat spiral fashion to reach, in rotation, their 

 respective positions at the dorsal end of each opercular 

 crescent. .A similar process was observed in SabeUaria 

 spinulosa, but in this species there are, in each lobe, two 

 or three long, curved, acicular dorsal chsetae in addition 

 to the three rows of ch^tae which form the operculum. 

 In certain members of the family, e.^. Pallasia, the 

 operculum is armed with only two rows of pale<-E, but 

 there exist, in addition, two or more hooks, placed dorsally, 

 in positions corresponding to the acicula above mentioned. 

 These hooks have been regarded by some zoologists as 

 homologous with the missing middle row of opercular 

 palea:>, but this view is rendered very doubtful by the 

 conditions found, and described above, in Sabellaria 

 spinulosa. 



The Anatomy and Physiology of Calma glaucoides. 

 Calma is a small nudibranch mollusc living exclusively 

 on the eggs of fishes, which it simulates closely in appear- 

 ance. Mr. T. J. Evans described the modifications which 

 this animal has undergone in response to its specialised 

 diet. The radula, a rasping instrument in other gastro- 

 pods, has become a saw for cutting open the eggs, the 

 teeth being reduced to a single row. The stomach is 

 enormously enlarged, and in well-fed specimens is filled 

 with a hard, albuminous mass. During the feeding period 

 the growth of the genital organs is retarded ; they do not 

 develop until the contents of the stomach have been 

 digested, by which time space is available for the growing 

 gonads. The gonads are not massed as in an ordinary 

 Eolid, but are packed in the angles between the liver 

 diverticula, and the male duct has been pushed forward 

 to the level of the mouth. There is no intestine or anus, 

 and- the excreta of the first year remain on the floor of 

 the stomach and liver branches under the food of the 

 second year. In the cerata certain amoeboid cells of the 

 ha^moccel enter into relations with the liver cells and 



NO. 2139, VOL. 84] 



absorb protein from them. When fully impregnated with 



nutritive material they fall back into the hasmoccel as 



oval glassy cells, and the protein contents are gradually 

 absorbed during the winter fast. 



Sex and Immunity. 

 Mr. GeofTrey Smith gave the results of further work 

 on the effects of the parasitic cirripede Sacculina on the 

 spider crab Inachus. He has previously shown that the 

 effect of the parasite is to cause the male host to assume 

 adult female characters externally, and, after the death 

 of the parasite, internally also, for large ova were pro- 

 duced in the testes. The effect of the parasite on the 

 young female crab is of a similar nature, for the young 

 infected female is forced to assume adult female characters 

 at a premature stage. Mr. Smith suggested an ingenious 

 explanation of these phenomena. He showed that, in an 

 infected Inachus of either sex, the Sacculina-roots manu- 

 facture yolk similar to the ovarian yolk of a normal 

 female Inachus. The parasite thus forces the crab, 

 whether male or female, to produce substances in the 

 blood from which the Sacculina-roots can manufacture 

 yolk ; as fast as these substances are produced the 

 Sacculina takes them up and, by anchoring them, stimu- 

 lates their continued production. These yolk-forming sub- 

 stances, saturating the body fluids of infected crabs, both 

 male and female, cause the development of the secondary 

 sexual characters. When the parasite dies and its roots 

 no longer assimilate the yolk-forming substances, they are 

 taken up by the remains of the gonad (which, while the 

 crab was parasitised, had been reduced and non-functional), 

 which consequently proceeds to form ova. In the parallel 

 case of Peltogaster, parasitic on Eupagurus, Mr. Potts 

 has shown that small ova are formed in the testes of the 

 host while the parasite is still alive, so that, in this case, 

 the excess of yolk-forming substances is taken up by the 

 gonad during the life of the parasite. This over-produc- 

 tion of a substance which is being anchored by a parasite 

 is regarded by Mr. Smith as closely analogous to the 

 production of antibody in immunisation. By supplying 

 the Sacculina with the yolk-forming substances, the crab 

 protects other nutritional substances necessary for its vital 

 organs from being abstracted by the parasite. 



In answer to comments by Prof. Bateson, F.R.S., and 

 Prof. Hartog, regarding the nature of the eggs found in 

 the testes of male crabs recovering from the attacks of 

 Sacculina, Mr. Smith stated that such ova are as large 

 and .as fully formed as normal eggs, become pigmented 

 (red) like the latter, and, so far as structure is concerned, 

 are entitled to be regarded as ordinary eggs. Replying 

 to observations by Mr. Doncaster regarding the presence 

 or absence of " femaleness " in the male crab, Mr. Smith 

 said that the conditions indicated that the male contains 

 latent female potentialities, for these latter could not be 

 introduced by the .Sacculina, and yet complete formation 

 of morphological female characters took place in recovering 

 males. 



The Colours of Insect Larvae. 



Prof. Walter Garstang described a series of e.xperimenl-^ 

 which he had carried out this summer on the effects of 

 foods deficient in chlorophyll on the coloration of phyto- 

 phagous larva; of Lepidoptera. The experiments were 

 designed to confirm and extend the results obtained in 

 1892 by Prof. Poulton, who showed that, in the case of 

 Tryphacna pronuba, larva; fed on the white mid-ribs of 

 cabbage retained a white ground colour (with the addition 

 of superficial black pigment in the later stages), while 

 larva; fed on yellow etiolated leaves developed the same 

 green and brown pigments as those fed on green leaves. 

 Prof. Garstang obtained very similar results, using the 

 larvas of Euplexia lacipara. Larvae fed from the time of 

 hatching on the yellow inner leaves of lettuce developed 

 the same green pigments as those fed on green leaves, 

 while larvae fed on the mid-ribs acquired a semi-trans- 

 parent whitish colour, very faintly tinged with green or 

 vellow. The superficial blackish markings developed in 

 all cases. 



On the other hand, the larvae of Mamestra brassicae 

 fed on mid-rib of lettuce and on carrot, while failing to 

 produce the normal green colours, also showed a marked 



